Summary of Harbor Porpoise 

(Phocoena phocoena) Bycatch 

and Levels of Compliance in the 

Northeast and Mid–Atlantic Gillnet 

Fisheries after the Implementation of the 

Take Reduction Plan: 1 January 1999 – 

31 May 2007

 

US DEPARTMENT OF COMMERCE 

National Oceanic and Atmospheric Administration 

National Marine Fisheries Service 

Northeast Fisheries Science Center 

Woods Hole, Massachusetts 

August 2008

NOAA Technical Memorandum NMFS-NE-212 
Recent Issues in This Series:

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211. Trends in Selected Northeast Region Marine Industries. By Eric M. Thunberg. July 2008. NTIS Access No _______. 
Summary of Harbor Porpoise (Phocoena 

phocoena) Bycatch and Levels of 

Compliance in the Northeast and Mid–

Atlantic Gillnet Fisheries after the 

Implementation of the Take Reduction Plan: 

1 January 1999 – 31 May 2007

Debra Palka1

Christopher D. Orphanides2 

Melissa L. Warden3

1

National Marine Fisheries Service, Northeast Fisheries Science Center, 166 Water Street, Woods Hole, MA 02543 

2

National Marine Fisheries Service, Northeast Fisheries Science Center, 28 Tarzwell Drive, Narragansett RI 02882 3

Integrated Statistics, Inc., 16 Sumner Street, Woods Hole, MA 02543 

US DEPARTMENT OF COMMERCE 

Carlos M. Gutierrez, Secretary 

National Oceanic and Atmospheric Administration 

Vice Admiral Conrad C. Lautenbacher, Jr., USN (ret.), Administrator 

National Marine Fisheries Service 

James W. Balsiger, Acting Assistant Administrator for Fisheries 

Northeast Fisheries Science Center 

Woods Hole, Massachusetts 

August 2008

NOAA Technical Memorandum NMFS-NE-212 

This series represents a secondary level of scientific publishing. All issues employ thorough internal 

scientific review; some issues employ external scientific review. Reviews are transparent collegial 

reviews, not anonymous peer reviews. All issues may be cited in formal scientific communications. 
Editorial Notes 

Information Quality Act Compliance: In accordance with section 515 of Public Law 106-554, the 

Northeast Fisheries Science Center completed both technical and policy reviews for this report. 

These predissemination reviews are on file at the NEFSC Editorial Office. 

Species Names: The NEFSC Editorial Office’s policy on the use of species names in all 

technical communications is generally to follow the American Fisheries Society’s lists of 

scientific and common names for fishes, mollusks, and decapod crustaceans and to follow the 

Society for Marine Mammalogy's guidance on scientific and common names for marine 

mammals. Exceptions to this policy occur when there are subsequent compelling revisions in the 

classifications of species, resulting in changes in the names of species. 

Statistical Terms: The NEFSC Editorial Office’s policy on the use of statistical terms in all 

technical communications is generally to follow the International Standards Organization’s 

handbook of statistical methods. 

Internet Availability: This issue of the NOAA Technical Memorandum NMFS-NE series is 

being published as a Web document in HTML and PDF formats and can be accessed at: 

http://www.nefsc.noaa.gov/nefsc/publications/. 
2

EXECUTIVE SUMMARY 

The Harbor Porpoise Take Reduction Plan (HPTRP), which went into effect on 1 January 1999, 

is a plan to reduce bycatch of harbor porpoises (Phocoena phocoena) in the Mid–Atlantic and 

Northeast gillnet fisheries. The plan requires a combination of time/area closures and gear 

modifications. The purpose of this paper is to document patterns of harbor porpoise bycatch, and 

levels of compliance to the HPTRP in the Mid-Atlantic fishery, divided into the southern mid–

Atlantic and New Jersey regions and in the Northeast fishery, divided into the Cape Cod and 

Gulf of Maine regions. Data were collected by the Northeast Fisheries Observer Program (1 

January 1999 – 31 May 2007). Bycatch rate patterns were explained in terms of gear 

characteristics, fishing practices, and environmental factors, as derived from regression models. 

In the southern mid–Atlantic region, eight harbor porpoise takes were observed February – April 

in 1999–2007. Four of the takes were in the ocean–intercept American shad (Alosa sapidissima) 

and river herring (Alosa chrysochloris) fishery, which is no longer operational. The other four 

takes were in large mesh gillnets (7–18 in) that were out of compliance with the HPTRP 

requirements. About 65% of the observed small mesh (>5–<7 in) hauls and 21% of the observed 

large mesh hauls were in compliance with the HPTRP. 

In the New Jersey region, 43 harbor porpoise takes were observed January – April in 1999–2007. 

They were in large mesh gillnets targeting monkfish (Leptoscopus americanus). About 77% of 

the observed small mesh gillnets and 40% of the observed large mesh gillnets were in 

compliance with the HPTRP. Bycatch rate patterns were best explained by a model that included 

(a) fixed environmental factors (bottom depth and distance to the 50 m depth contour) which 

indicate the location of the takes; (b) varying environmental factors (surface and bottom water 

temperatures and winter North Atlantic Oscillation [NAO] index values) which explain annual 

and monthly differences; and (c) fishing characteristics (ship’s gross tonnage, anchor weight, 

number of anchors used, and time duration the gillnet was in the water [i.e., soak duration]). 

In the Cape Cod region, 87 harbor porpoise takes were observed during December – May in 

1999–2007, of which 63 were outside of the HPTRP’s Cape Cod South management area. In this 

region during the time pingers were required, 45% used the required number of pingers, 40% did 

not use any pingers, and 15% used pingers but less than the required number of pingers. Bycatch 

rates of hauls that used pingers were about half that of hauls that did not use pingers: 0.053 

versus 0.098 harbor porpoises per metric tons landed, respectively. Bycatch rate patterns in this 

region were best explained by a model that included fixed time and area characteristics (steam 

time, home state, and day of the year) and gear characteristics (twine size). 

In the Gulf of Maine region, 104 harbor porpoise takes were observed during all months of the 

year in 1999–2007. The highest average bycatch rates were in February and November. 

Compliance with the seasonal HPTRP’s pinger requirements was highest in 1999 (about 75%), 

dropped to a low in 2003 and 2004 (about 10%), and started rising again in the first quarter of 

2007 (about 60%). Bycatch rate patterns were best explained by a model that included (a) fixed 

areas (Management Area); (b) environmental factors (sea surface temperature [SST], and NAO) 

which explain annual and monthly variations; and (c) gear characteristics (average mesh size and 

leadline total weight) which indicate types of gillnets with higher bycatch rates. 
3

TABLE OF CONTENTS 

Executive summary......................................................................................................................... 2 

Table of contents............................................................................................................................. 3 

1. General overview and methods................................................................................................... 4 

1.1 Introduction........................................................................................................................... 4 

1.2 Data....................................................................................................................................... 5 

1.3 Analysis methods.................................................................................................................. 5 

1.3.1 Observer coverage ......................................................................................................... 5 

1.3.2 General patterns ............................................................................................................. 5 

1.3.3 Compliance .................................................................................................................... 6 

1.3.4 Correlated factors........................................................................................................... 6 

2. Southern mid–Atlantic region................................................................................................... 11 

2.1 Summary............................................................................................................................. 11 

2.2 Observer coverage .............................................................................................................. 11 

2.3 General bycatch patterns..................................................................................................... 11 

2.4 Compliance ......................................................................................................................... 12 

2.4.1 Small mesh................................................................................................................... 12 

2.4.2 Large mesh................................................................................................................... 12 

2.5 Correlated factors................................................................................................................ 13 

3. New Jersey region..................................................................................................................... 20 

3.1 Summary............................................................................................................................. 20 

3.2 Observer coverage .............................................................................................................. 20 

3.3 General bycatch patterns..................................................................................................... 21 

3.4 Compliance ......................................................................................................................... 21 

3.4.1 Small mesh................................................................................................................... 21 

3.4.2 Large mesh................................................................................................................... 22 

3.5 Correlated factors................................................................................................................ 22 

3.5.1 Fixed environmental factors ........................................................................................ 23 

3.5.2 Varying environmental factors .................................................................................... 23 

3.5.3 Gear and fishing characteristic factors......................................................................... 23 

4. Cape Cod region ....................................................................................................................... 43 

4.1 Summary............................................................................................................................. 43 

4.2 Observer coverage .............................................................................................................. 43 

4.3 General bycatch patterns..................................................................................................... 44 

4.4 Compliance ......................................................................................................................... 44 

4.5 Correlated factors................................................................................................................ 45 

5. Gulf of Maine region ................................................................................................................ 61 

5.1 Summary............................................................................................................................. 61 

5.2 Observer coverage .............................................................................................................. 61 

5.3 General bycatch patterns..................................................................................................... 61 

5.4 Compliance ......................................................................................................................... 62 

5.5 Correlated factors................................................................................................................ 63 

References..................................................................................................................................... 85 

Appendix....................................................................................................................................... 86 
4

1. GENERAL OVERVIEW AND METHODS 

1.1 Introduction 

The Harbor Porpoise Take Reduction Plan (HPTRP) went into effect on 1 January 1999 (63 FR 

66464, 2 December 1998). The purpose of this plan is to reduce the serious injury and mortality 

of the Gulf of Maine/Bay of Fundy harbor porpoises (Phocoena phocoena) from incidental 

interactions with the Mid–Atlantic and Northeast gillnet fisheries, where these two fisheries were 

defined in the List of Fisheries (72 FR 66048, 27 November 2007). 

For the Mid–Atlantic gillnet fishery, which operates to the west of the 72°30’W longitude line 

and south of Long Island, NY, the HPTRP defines three management areas (MA): the southern 

mid–Atlantic MA, Mudhole MA, and Waters off New Jersey (excluding the Mudhole) MA 

(Figure 1). The HPTRP has different regulations for gillnets made with “large mesh” (7–18 in) 

and “small mesh” (>5–<7 in). Gillnets using other mesh sizes are not managed under the 

HPTRP. The HPTRP regulations include complete closures to all gillnets in some times and 

areas, and they include restrictions in gillnet string lengths, twine sizes and tie downs in other 

times and areas (Table 1). 

For the Northeast gillnet fishery, which operates to the north and east of the 72°30’W longitude 

line, the HPTRP defines six management areas: the Cape Cod South MA, Massachusetts Bay 

MA, Mid–Coast MA, Northeast MA, Offshore MA, and Cashes Ledge MA (Figure 1). These 

management areas, for specified time periods, are either completely closed to all gillnets or 

closed to all gillnets that do not use pingers1

 (Table 2). Two other areas of interest relative to the 

bycatch of harbor porpoises include: (1) the Western Gulf of Maine Closure Area (WGOM CA), 

which is a multispecies fishery management area implemented 1 May 1998 that is closed year 

round to all fishing gear types (63 FR 15326, 31 March 19982); and (2) an area discussed by the 

Harbor Porpoise Take Reduction Team (HPTRT) for potential future management under a 

revised HPTRP, which will be referred to as the Stellwagen Bank Area. Note, in this 

manuscript, the terms “closure area” and “CA” indicate an area that is closed year round to 

fishing; the terms “management area” and “MA” indicate an area defined in the HPTRP which 

requires bycatch mitigation measures to reduce harbor porpoise bycatch, and the term “area” is a 

more general term which can indicate a closed area, a management area, or an area that is not 

managed. 

This paper investigates harbor porpoise bycatch in the Mid–Atlantic and Northeast gillnet 

fisheries after the HPTRP was implemented. To aid in describing bycatch patterns and because 

of differences in fishing practices and harbor porpoise habitat usage, the two fisheries were 

divided into two regions (Figure 1). The Mid–Atlantic gillnet fishery was divided into the 

southern Mid–Atlantic and New Jersey regions. The Northeast gillnet fishery was divided into 

the Cape Cod and Gulf of Maine regions. Data collected from 1 January 1999 – 31 May 2007 

by the Northeast Fisheries Observer Program (NEFOP) were used to describe, within each 

region, the general patterns in harbor porpoise bycatch; levels of compliance with the HPTRP 

 

1

 A pinger is defined as an acoustic deterrent device which, when immersed in water, broadcasts a 10 kHz (± 2 kHz) 

sound at 132 dB (± 4 dB) re 1 micropascal at 1 m, lasting 300 milliseconds (± 15 milliseconds) and repeating every 

4 seconds (± 2 seconds). 

2

 This multispecies fishery management action also implemented other closure areas, but only the WGOM Closure 

Area was discussed by the harbor porpoise take reduction team. 
5

mitigation measures; and bycatch rate patterns as related to space and time, gear characteristics, 

fishing practices, and environmental factors. 

1.2 Data 

Observers from NEFOP collect data on characteristics of the trip, haul, gear, economic factors, 

catch, and incidental bycatch (NEFSC 2008). Only bycatch of dead harbor porpoises and only 

observed hauls that have complete location information were used. The factors collected by 

NEFOP that were used in these investigations are described in the appendix. Annual percent 

observer coverage (in terms of metric tons (mtons) landed) for the Mid–Atlantic gillnet fishery 

has been 1–5%, which is generally lower than the coverage in the Northeast gillnet fishery, 1-7% 

(Figure 2). 

Environmental factors associated with the location and date of the observed haul were added to 

the data collected through 2006: bottom depth and slope, distance between the location of the 

haul and the coastline and various depth contours, sea surface and bottom water temperatures, 

North Atlantic oscillation (NAO) index value, chlorophyll α concentration, and sediment type 

(Appendix). Data from 2007 were still preliminary and had not been processed as completely as 

the older data. For details on the processing and inclusion of environmental data see Warden and 

Orphanides (2008). 

For many factors collected before January 2007 (flagged in appendix), missing values were filled 

in with the next best available value. Most of these factors had less than 4% missing values, 

many less than 1%. For those values that were missing, a hierarchy of replacement strata was 

established, varying to some degree on the factor in question. Generally, missing values were 

filled in with a value from the same trip, if available. If not available, then a stratified median 

value based on a combination of vessel, gear type, month, and year was used to fill in the 

missing values. For missing depth and water temperature values collected by the observers, 

depth and sea surface temperature (SST) sampled from GIS datasets were used as replacement 

values, followed by stratified medians. For more details on the imputation of missing values, see 

Warden and Orphanides (2008). 

The above process left most factors with less than 0.5% missing values. For factors that were not 

filled in or were collected in 2007, the S–PLUS function na.gam.replace was used to fill in the 

missing value. That is, within each region’s data, missing values for continuous factors were 

replaced with the mean of the factor’s values that were not missing, and for categorical factors, 

an additional missing value level of the factor was created. 

1.3 Analysis Methods 

1.3.1 Observer coverage 

For each region, the number of observed hauls, trips, and vessels were documented from 1 

January 1999 – 31 May 2007. In addition for each region, further analyses were performed only 

on data collected during the months when harbor porpoises are typically in the region, which 

usually corresponded to the months with documented takes. 

1.3.2 General patterns 

For each region, the following was described: general patterns of where and when the fishery 

was observed; general spatial–temporal patterns of the harbor porpoise bycatch; and bycatch 

rates for various levels of gear characteristics, fishing practices, and environmental factors. 
6

1.3.3 Compliance 

For each region, the percent of hauls that were compliant with each individual mitigation 

measure and the percent of hauls that were completely in compliance were calculated. 

1.3.4 Correlated factors 

For each region, a model was developed to identify which location factors, gear characteristics, 

fishing practices, and environmental factors were most highly correlated to the bycatch rate. 

These factors were regressed against the bycatch rate by using generalized additive models (if 

the factor was continuous) or by using generalized linear models (if the factor was categorical), 

assuming a quasi–Poisson distribution3

, using S–PLUS version 7.0 for Microsoft Windows. The 

bycatch rate was defined as the total observed number of dead harbor porpoises per total amount 

of observed landings, where landings were reported in metric tons4 + 0.0015. 

Generalized additive models allow a nonlinear relationship between the factor and bycatch rate, 

if the data support a nonlinear relationship. A forward stepwise selection method was employed, 

using the Akaike Information Criterion (AIC) as the selection criterion, where a model with a 

smaller AIC fits the data better than a model with a larger AIC. The forward stepwise selection 

method was as follows. First, all factors were individually regressed against the bycatch rate. 

The most highly significant factor identified was used to create a 1–factor model. Then all other 

factors were individually added to the 1–factor model to identify the next most significant factor, 

which was then added to the 1–factor model to create a 2–factor model. This process continued 

until the AIC did not decrease by at least 2%, thus resulting in the best fitting model. 

 

3

 A Poisson distribution was used because the numbers of observed takes were counts ranging from 1 – 4 animals 

per observed haul. This distribution assumes equal–dispersion; that is, the variance of the bycatch rate is equal to the 

mean of the bycatch rate. Because this assumption may not always be valid, a quasi–Poisson distribution was used 

to properly account for over– or under–dispersion, if it was needed. 

4

 The factor metric tons landed is the only factor available that can be used as a unit of effort to expand a bycatch 

rate from an observed sample of the gillnet fishery into a bycatch estimate for the entire gillnet fishery. 5

 For each haul 0.001 metric tons of landings was added to the recorded landings to ensure the amount of landings 

for each haul was greater than zero. 
7

Table 1. Management measures for large and small mesh gillnets in the Mid–Atlantic gillnet 

fishery, which includes three harbor porpoise take reduction plan’s management areas (MA).

LARGE MESH FISHERY (7–18 in) 

Floatline length: 

 Mudhole MA and southern mid–Atlantic MA ≤ 3,900 ft 

 Waters off New Jersey (excluding the Mudhole) MA ≤ 4,800 ft 

Twine size ≥ 0.90 mm 

Tie downs Required 

Net number per vessel 80 gillnets 

Net size ≤ 300 ft 

Net tagging Required 

Number of gillnets within a gillnet string: 

 Mudhole MA and southern mid-Atlantic MA ≤ 13 gillnets 

 Waters off New Jersey (excluding the Mudhole) MA ≤ 16 gillnets 

Time/area closures: 

 Waters off New Jersey, including the Mudhole, MAs Closed 1–20 April 

 Mudhole MA and southern mid–Atlantic MA Closed 15 February – 15 March 

Gear modification requirements: 

 Waters off New Jersey (excluding the Mudhole) MA 

1 January – 30 March and 21 – 30 

April 

 Mudhole MA 

1 January – 14 February; 16 

March – 31 March; and 21 – 30 

April 

 southern mid–Atlantic MA 

1 February – 14 February and 16 

March – 30 April 

SMALL MESH FISHERY (> 5–< 7 in) 

Floatline length: 

 Waters off New Jersey, including the Mudhole, MAs ≤ 3,000 ft 

 southern mid–Atlantic MA ≤ 2,118 ft 

Twine size ≥ 0.81 mm 

Tie downs Prohibited 

Net number per vessel 45 gillnets 

Net size ≤ 300 ft 

Net tagging Required 

Number of gillnets within a gillnet string: 

 Waters off New Jersey, including the Mudhole, MAs ≤ 10 gillnets 

 southern mid–Atlantic MA ≤ 7 gillnets 

Time/area closures: 

 Mudhole MA Closed 15 February – 15 March 

Gear modification requirements: 

 Waters off New Jersey (excluding Mudhole) MA 1 January – 30 April 

 Mudhole MA 

1 January – 14 February and 16 

March – 30 April 

 southern mid–Atlantic MA 1 February – 30 April 
8

Table 2. Times and areas in the Northeast gillnet fishery that are either closed to all gillnets 

(Closed) or closed to all gillnets that do not use pingers (Closed – pingers allowed). Note that 

only the areas that are considered in this paper are included below (e.g., not all of the 

Multispecies Fishery Management Plan management areas (MA) and closed areas (CA) are 

included).

AREA DATES STATUS OF GILLNETS 

Northeast MA 15 August – 13 September Closed 

Mid–coast MA 15 September – 31 May Closed – pingers1 allowed 

1 December – 28/29 

February Closed – pingers allowed 

1 – 31 March Closed 

Massachusetts Bay 

MA 

1 April – 31 May Closed – pingers allowed 

Offshore MA 1 November – 31 May Closed – pingers allowed 

Cashes Ledge MA 1 – 28/29 February Closed 

Western Gulf of 

Maine CA All year round Closed 

1 December – 28/29 

February Closed – pingers allowed 

1 – 31 March Closed 

Cape Cod South MA 

1 April – 31 May Closed – pingers allowed 

1

 A pinger is defined as an acoustic deterrent device which, when immersed in water, broadcasts 

a 10kHz (± 2kHz) sound at 132dB (± 4dB) re 1 micropascal at 1m, lasting 300 milliseconds (± 

15 milliseconds), and repeating every 4 seconds (± 2 seconds). 
9

Figure 1. Location of management areas (MA) under the harbor porpoise (phocena phocena) take 

reduction plan, Western Gulf of Maine Closure Area (WGOM CA) and Stellwagen Bank Area. In the 

insert are locations of the two regions in the Northeast gillnet fishery (Gulf of Maine and Cape Cod 

regions) and two regions in the Mid-Atlantic gillnet fishery (New Jersey and southern mid–Atlantic 

regions), which are all located within the US Exclusive Economic Zone (EEZ). 
10

1990 1992 1994 1996 1998 2000 2002 2004 2006

Year

1

2

3

4

5

6

7 Northeast gillnet fishery

mid-Atlantic gillnet fishery

Percent observer coverage

Figure 2. Percent observer coverage (in terms of mtons landed) by year in the Mid–Atlantic and 

Northeast gillnet fisheries.
11

2. SOUTHERN MID–ATLANTIC REGION

2.1 Summary 

The southern mid-Atlantic region (Figure 1) is the southern portion of the Mid–Atlantic gillnet 

fishery and is the southern mid-Atlantic MA under the HPTRP. Since the implementation of the 

HPTRP on 1 January 1999, harbor porpoise bycatch in waters in the southern mid–Atlantic 

region has been relatively low. Takes were observed February – April from 1999–2007. Out of 

the 4,673 observed gillnet hauls, 8 harbor porpoise takes were observed. Takes were observed in 

gillnets targeting American shad (Alosa sapidissima), monkfish (Leptoscopus americanus), and 

striped bass (Morone saxatilis). Bycatch rates were highest in March. 

Four observed hauls with takes used very small mesh sizes (≤5 in), which are not managed under 

the HPTRP. These hauls targeted American shad in March 1999 or March 2000, used twine 

sizes of 0.81 or 0.52 mm in strings that were 600 ft or less. The ocean–intercept American shad 

and river herring (Alosa chrysochloris) fishery was slowly phased out starting in 2000 and has 

been completely closed since 2005. 

Four observed hauls with takes used large mesh sizes (7–18 in), targeted monkfish or striped 

bass, and used twine sizes of 0.66 or 0.9 mm in strings that were 1,200–4,500 ft. One take was 

observed in February, one in March, and two in April. All four of these large mesh hauls with 

takes were out of compliance with the HPTRP. 

About 65% of the observed small mesh hauls (>5–<7 in) were completely in compliance. No 

harbor porpoise takes were observed in small mesh gillnets in this time and area. Most of the 

hauls that were out of compliance used twine sizes that were too small. 

About 21% of the observed large mesh hauls were completely in compliance. Most of the hauls 

that were out of compliance used twine sizes that were too small. About half of the observed 

large mesh hauls did not use tie downs, as the HPTRP requires. About 30% of the observed 

large mesh hauls were fished during the time period closed to all large mesh gillnets, 15 

February – 15 March.

2.2 Observer Coverage 

In the southern mid–Atlantic region (Figure 1) from 1 January 1999 – 31 May 2007, there were 

observed hauls year round, with the least number of observed hauls per month in the summer, 

June – August (Figure 3). Harbor porpoise bycatch was observed only during February – April 

(Figure 4), the same time period this region is regulated by the HPTRP. Thus, further analyses 

focused on the southern mid–Atlantic region include only the months February – April. 

In the southern mid–Atlantic region from February – April of the years 1999–2007 (Figure 5), 

there were 4,673 hauls observed, which were from 930 trips and 214 vessels. These totals are 

from 271–782 hauls observed per year, which were from 54–169 trips per year and from 26–66 

vessels per year (Table 3). 

2.3 General Bycatch Patterns 

Of the 4,673 hauls observed February – April in 1999–2007, eight hauls each took a single 

harbor porpoise. The bycatch rates were highest in March (Table 4). 
12

Four of the observed takes were in strings using very small mesh sizes (≤5 in), and the other four 

were in strings using large mesh sizes (7–18 in). The very small mesh sizes are not managed 

under the HPTRP. The bycatch rate was nearly three times higher in the observed large mesh 

strings than in the observed very small mesh strings: 0.0095 versus 0.0279 harbor porpoises per 

mtons landed (Table 4; Figure 6). 

The four observed hauls using very small mesh sizes that had takes targeted American shad in 

1999 or 2000, used twine sizes of 0.81 or 0.52 mm in strings that were 600 ft or less, and 

occurred in March. 

The four observed hauls using large mesh sizes that had takes targeted monkfish or striped bass, 

and used twine sizes of 0.66 or 0.9 mm in strings 1200–4500 ft long. One take occurred in 

February, one in March, and two in April. All of these large mesh hauls with takes were out of 

compliance with the HPTRP (see details below). 

2.4 Compliance 

2.4.1 Small mesh 

From February – April of 1999–2007, there were 721 observed hauls (from 184 trips and 85 

vessels) that used small mesh in the southern mid–Atlantic region. No harbor porpoise takes 

were observed in small mesh gillnets in this time and area. Overall, about 65% of the observed 

hauls using small mesh were completely in compliance (Table 5). 

Looking only at the gear length requirement, there were 53 (7.4%) hauls (20 trips from 14 

vessels) that were using small mesh sizes (5.3 – 6.5 in) and had total gear lengths greater than 

2,118 ft, the limit set in the HPTRP. The lengths ranged from 2,160 – 6,600 ft. The 53 hauls 

were observed in each month and during most years: February (15), March (23) and April (15), 

and in 1999 (24), 2000 (8), 2003 (3), 2004 (5) and 2007 (13). These out of compliance hauls 

were targeting a variety of species: bluefish (Pomatomus saltatrix; 1), smooth dogfish (Mustelus 

canis; 15), spiny dogfish (Squalus acanthias; 32), and summer flounder (Paralichthys dentatus; 

5). 

Looking only at the twine size requirements, there were 206 hauls (29%) from 54 trips and 33 

vessels that used small mesh (5.1 – 6.5 in) and twine sizes less than 0.81 mm, the limit set in the 

HPTRP (0.47 – 0.74 mm). The 206 hauls were observed in each month and during most years: 

February (32), March (69), and April (105) and in 1999 (32), 2000 (67), 2001 (10), 2002 (3), 

2003 (6), 2004 (8), 2005 (41), and 2007 (39). These out of compliance hauls were targeting a 

variety of species: shads (American shad and herring; Clupeidae), Atlantic croaker 

(Micropogonias undulatus), bluefish, kingfish (Menticirrhus sp), red drum (Sciaenops ocellatus), 

smooth dogfish, spiny dogfish, striped bass, southern flounder (Paralichthys lethostigma), 

summer flounder, and weakfish (Cynoscion regalis).

2.4.2 Large mesh 

From February – April of 1999 – 2007, there were 874 observed hauls (from 229 trips and 45 

vessels) that used large mesh in the southern mid–Atlantic region. Overall, only 21% of the 

observed hauls using large mesh were completely in compliance (Table 5). Four harbor 

porpoises were observed taken in large mesh gillnets, and all of these hauls were out of 

compliance. 
13

Looking only at the gear length requirements, in the southern mid–Atlantic region during 

February – April, there were 198 hauls (23%) from 69 trips and 17 unique vessels that used large 

mesh and floatline lengths greater than 3,900 ft, the limit set in the HPTRP (4,200–6,000 ft). 

The 198 hauls were observed mostly in April and in most years: February (3), March (12), and 

April (183) and in 1999 (2), 2001 (77), 2002 (88), 2004 (14), 2005 (3), and 2007 (14). All of 

these out of compliance hauls were targeting monkfish. 

Looking only at the twine size requirements, there were 90 hauls (10%) from 32 trips and 18 

vessels that used large mesh (7–8 in) and twine sizes less than 0.9mm, the limit set in the HPTRP 

(0.47–0.81 mm). The 90 hauls were observed in each month and in most years: February (29), 

March (37), and April (24), and in 1999 (16), 2000 (13), 2001 (18), 2002 (4), 2003 (1), 2004 (5), 

2005 (2), 2006 (3), and 2007 (28). These out of compliance hauls were targeting monkfish (43), 

smooth dogfish (5) and striped bass (42). 

Looking only at the closure requirements for large mesh, there were 251 observed hauls (30%) 

using large mesh in the southern mid–Atlantic region during the closed period, 15 February – 15 

March. 

Looking only at the requirement to use tie downs, there were 473 (54%) observed hauls (from 

108 trips and 23 unique vessels) that did not use tie downs. 

2.5 Correlated Factors 

Because there were only eight takes, a bycatch rate model was not developed. 
14

Table 3. Descriptive statistics about the bycatch of harbor porpoises (Phocoena phocoena) in the 

southern mid–Atlantic region February – April of 1999–2007.

Year 

 1999 2000 2001 2002 2003 2004 2005 2006 2007 Total 

Number of observed 

hauls 698 782 776 456 271 371 377 313 629 4673

Number of observed 

trips 129 150 169 80 54 81 87 59 121 930

Number of observed 

vessels 56 57 43 26 33 50 50 34 66 214

Number of observed 

hauls with one or more 

takes 3 1 1 0 0 2 0 0 1 8

Total number of 

observed takes 3 1 1 0 0 2 0 0 1 8

Bycatch rate (observed 

takes/observed number 

of hauls) 0.004 0.001 0.001 0 0 0.005 0 0 0.002 0.002

Bycatch rate (observed 

takes/observed mtons 

landed) 0.028 0.008 0.008 0 0 0.026 0 0 0.009 0.010

Table 4. Using observer data from February – April, 1999–2007 in the southern mid–Atlantic 

region, the number of observed hauls and takes of harbor porpoises (Phocoena phocoena), and 

the resulting bycatch rates by month and by mesh size (in inches). 

Month Mesh size 

 Feb Mar Apr

Very small

≤ 5 in

Small

>5 – <7 in

Large 

7–18 in Unknown

Number of 

observed 

hauls 1369 1592 1712 3005 721 878 69

Number of 

observed takes 1 5 2 4 0 4 0

Bycatch rate 

(observed 

takes/observed 

hauls) 0.001 0.003 0.001 0.001 0 0.005 0

Bycatch rate 

(observed 

takes/observed 

mtons landed) 0.004 0.016 0.010 0.010 0 0.028 0
15

Table 5. Number of observed hauls and takes of harbor porpoises (Phocoena phocoena) in 

gillnets that were in and out of compliance from the southern mid–Atlantic region February – 

April, 1999–2007. Note, any one haul could have been out of compliance for one or more of the 

requirements. 

Large mesh is 7–18 in; small mesh is >5–<7 in; and very small mesh (not regulated in HPTRP) is 

≤5 in. 

ALL HAULS 

In 

compliance? 1999 2000 2001 2002 2003 2004 2005 2006 2007 Total

No 125 138 219 182 45 50 88 10 92 949

Yes 573 644 557 274 226 321 289 303 537 3724

% compliant 82 82 72 60 83 87 77 97 85 80

Number of hauls TOTAL 698 782 776 456 271 371 377 313 629 4673

No 0 0 1 0 0 2 0 0 1 4

Yes 3 1 0 0 0 0 0 0 0 4

Number of takes TOTAL 3 1 1 0 0 2 0 0 1 8

 

SMALL MESH 

In 

compliance? 1999 2000 2001 2002 2003 2004 2005 2006 2007 Total

No 56 74 10 3 9 13 41 0 47 253

Yes 152 136 44 40 12 14 1 13 56 468

% compliant 73 65 82 93 57 52 2 100 54 65

Number of hauls TOTAL 208 210 54 43 21 27 42 13 103 721

No 0 0 0 0 0 0 0 0 0 0

Yes 0 0 0 0 0 0 0 0 0 0

Number of takes TOTAL 0 0 0 0 0 0 0 0 0 0

 

LARGE MESH 

In 

compliance? 1999 2000 2001 2002 2003 2004 2005 2006 2007 Total

No 69 64 208 179 36 35 47 10 44 692

Yes 0 0 102 2 3 7 4 46 18 182

% compliant 0 0 33 1 8 17 8 82 29 21

Number of hauls TOTAL 69 64 310 181 39 42 51 56 62 874

No 0 0 1 0 0 2 0 0 1 4

Yes 0 0 0 0 0 0 0 0 0 0

Number of takes TOTAL 0 0 1 0 0 2 0 0 1 4

 

VERY SMALL Not regulated 1999 2000 2001 2002 2003 2004 2005 2006 2007 Total

Number of hauls Not regulated 396 507 411 232 211 300 284 244 416 3078

Number of takes Not regulated 3 1 0 0 0 0 0 0 0 4
16

January

February

March

April

May

June

July

August

September

October

November

December

month

0

50

100

150

200

250

300

350

400

450

500

550

1999

2000

2001

2002

2003

2004

2005

2006

2007

average

Number of observed hauls

Figure 3. By year, number of observed hauls in the southern mid–Atlantic region 1 January 1999 – 

31 May 2007. 
17

Figure 4. Location of hauls in the southern mid-Atlantic management area (shaded blue) by month 

(colored dots) and hauls with observed harbor porpoise (Phocoena phocoena) takes (diamonds). 

Data used were from February – April in 1999–2007. Depth contours are 30, 50, and 100 m. 
18

Figure 5. Location of hauls in the southern mid-Atlantic management area (shaded blue) by year 

(colored dot) and hauls with observed harbor porpoises (Phocoena phocoena) takes (diamonds). 

Data used were from February – April in 1999–2007. Depth contours are 30, 50, and 100 m. 
19

Figure 6. Location of hauls in the southern mid–Atlantic management area (shaded blue), by mesh 

size categories (colored dot) and hauls with observed harbor porpoise (Phocoena phocoena) 

takes (diamonds). Data used were from February – April in 1999–2007. Depth contours are 30, 50, 

and 100 m. 
20

3. NEW JERSEY REGION

3.1 Summary 

The New Jersey region (Figure 1) is the northern portion of the Mid-Atlantic gillnet fishery and 

is the area covered by two HPTRP management areas, the Mudhole MA and Waters off New 

Jersey (excluding the Mudhole) MA. Since the implementation of the HPTRP, NEFOP observed 

43 harbor porpoises taken in gillnets in the New Jersey region. Most of these takes occurred in 

and around Hudson Canyon. All the takes were in large mesh gillnets that were targeting 

monkfish. Harbor porpoise bycatch in winter (January – April) in the New Jersey region 

increased dramatically in the last few years, particularly in 2005 and 2006. 

Less than half (40%) of the large mesh gillnets observed were in compliance with the HPTRP, 

where the length of the strings was the most common regulation measure that was out of 

compliance. The level of compliance during 2007 improved markedly over the previous four 

years. Bycatch rates of strings greater than 4,000 ft were three times greater than the rates for 

strings less than 4,000 ft. Over all years, about 77% of the small mesh gillnets were in 

compliance with the HPTRP, and nearly all of the observed small mesh gillnets during 2006 and 

2007 were in compliance. 

A statistical model that best predicted the bycatch rates in this region included fixed 

environmental factors (bottom depth and distance to the 50 m depth contour), varying 

environmental factors (sea surface and bottom water temperatures and winter North Atlantic 

Oscillation [NAO] index value), and fishery characteristics (ship’s gross tonnage, anchor weight, 

number of anchors on the gillnet, and duration of time the gillnet was in the water [i.e., soak 

duration]). One interpretation of these factors is that (1) fixed environmental factors indicated 

the general location of the majority of the takes (i.e., in and around Hudson Canyon), (2) varying 

environmental factors helped explain the annual and monthly differences in bycatch rates, and 

(3) fishing characteristics indicated the types of strings with higher bycatch. 

All of the observed takes were in gillnets that soaked for 48 or more hours; 63% of the observed 

hauls and 81% of the observed landings (mtons) were from gillnets that soaked for 48 or more 

hours. The bycatch rate of gillnets that soaked for more than one week was five times greater 

than for gillnets that soaked for less than one week. 

Investigating the fishing characteristic factors in these models further showed that the bycatch 

rate of the hauls that used four anchors was 100 times larger than that for hauls that used two 

anchors. The hauls that used four anchors had long soak durations (greater than 6.5 days), and 

when the soak duration was shorter than 6.5 days, the wind speeds were fairly high (greater than 

13.5 knots). Thus, gillnets with four anchors appear to be correlated to high bycatch rates not 

because of a cause and effect relationship between number of anchors and harbor porpoise 

bycatch, but because of the small sample of observed hauls with four anchors (only 77 hauls) and 

the high correlation between the number of anchors and soak duration. This can be interpreted 

as a statistical correlation between bycatch rates and the number of anchors, where the driving 

reason for the correlation is most likely the location of the haul and the soak duration. 

3.2 Observer Coverage 

In the New Jersey region (Figure 1), from 1 January 1999 – 31 May 2007, the number of 

observed hauls per month for this region ranged from 0 to about 140 hauls per month, with an 
21

average of 34 hauls per month (Figure 7). All observed harbor porpoise takes were documented 

January – April, the same time period this region is managed by the HPTRP. Thus, further 

analyses focused on hauls observed in the New Jersey region January – April in 1999–2007. 

In this region and time period, there were 721 hauls observed, which were from 202 trips and 

119 vessels. This represents 7–201 hauls observed per year, 2–61 trips per year, and from 1–32 

vessels per year (Table 6). 

3.3 General Bycatch Patterns 

Most of the harbor porpoise bycatch was near Hudson Canyon, both inside and outside of the 

Mudhole MA (Figure 8). Takes from the different years were located in similar areas. Of the 721 

hauls observed in the New Jersey region January – April, 691 hauls did not have any harbor 

porpoise bycatch, 22 hauls had 1 take, 4 hauls had 2 takes, 3 hauls had 3 takes, and 1 haul had 4 

harbor porpoise takes. Most of the hauls that took more than one harbor porpoise were in deeper 

waters, 40–50 m (Figure 9). 

Bycatch rates were highest in 2005 and 2006 (Table 6). All of the takes were from hauls that 

were targeting monkfish in large mesh gillnets, where 60% of the observed hauls (with and 

without takes) were targeting monkfish. There were no observed takes January – April 2007. 

The bycatch rate in February (0.775 harbor porpoises per mtons landed) was considerably higher 

than the rate in other months, 0–0.109 harbor porpoises per mtons landed (Table 7). 

Bycatch rates (numbers of observed hauls with one or more harbor porpoises per observed mtons 

landed) for categorizations of many factors are listed in Table 8. Categories with high bycatch 

rates include: the year 2006, the month of February, waters 60–100 fathoms (fa) deep, hauls 

targeting monkfish, surface water temperatures of 2–4oC, a fairly steeply sloped bottom, long 

soak durations (greater than 200 hrs), long string lengths (greater than 4,000 ft), tie downs with a 

length of 3–4 ft, gillnets that used four anchors weighing 80–100 lbs, years with a small winter 

NAO index value, leadlines fished at 30–50 fa depth, and waters with low concentrations of 

chlorophyll. 

3.4 Compliance 

3.4.1 Small mesh

From January – April in 1999–2007, 133 observed hauls (from 42 trips and 25 vessels) used 

small mesh gillnets in the New Jersey region, where only one observed haul was in the Mudhole 

MA. No harbor porpoise takes were observed in small mesh gillnets in the New Jersey region 

(Table 9). 

Looking only at the gear length requirement, in 1999 there were 23 observed hauls (12 trips from 

6 vessels) that were using small mesh sizes (5.5, 6, and 6.5 in) and had total string lengths greater 

than 3,000 ft (the limit set in the HPTRP). The string lengths ranged from 3,027–4,200 ft. Of 

these 23 hauls, 9 hauls from 6 trips had total string lengths that were 3,027–3,036 ft, which were 

3,000 ft of gillnetting plus the spaces between the gillnets. These nine hauls will be considered 

in compliance in this manuscript, since the differences in string lengths is simply the gaps 

between the gillnet panels. The 23 hauls occurred in January (3), February (1), March (9), and 

April (10). 
22

Looking only at the twine size requirements, the hauls out of compliance were observed during 

2004 (15 hauls, 3 trips, and 2 vessels) and 2006 (1 haul). These hauls used small mesh (5.5 in) 

and twine sizes of 0.4–0.7 mm, which are less than 0.81 mm, the limit set in the HPTRP. 

No other observed small mesh gillnets in the New Jersey region were out of compliance. 

3.4.2 Large mesh 

From January – April in 1999–2007, 119 observed hauls (from 36 trips and 21 vessels) used 

large mesh in the Mudhole MA, and 316 observed hauls (from 108 trips and 54 vessels) used 

large mesh in the Waters off New Jersey (excluding the Mudhole) MA. The level of compliance 

increased markedly in 2007 over that from the previous four years (Table 9). 

Looking only at the gear length requirements, in the Mudhole MA there were 62 (52%) observed 

hauls (23 trips and 14 unique vessels) that used large mesh and string lengths greater than 3,900 

ft (4,500–8,400 ft), which were out of compliance (Table 10). These occurred in 2002, 2003, 

and 2005–2007 (Table 10). In the Waters off New Jersey (excluding the Mudhole) MA, there 

were 163 (52%) observed hauls (70 trips and 36 unique vessels) that used string lengths greater 

than 4,800 ft (5,100–12,000 ft), which were out of compliance. These hauls occurred in 1999, 

2001, and 2003–2007. 

Looking only at the closure requirements, there were six observed hauls in 2001 and 2006 in the 

Mudhole MA and Waters off New Jersey (excluding the Mudhole) MA during the closed period 

(1–20 April); these hauls caught a total of three harbor porpoises (Table 10). Additionally, there 

was one observed haul in the Mudhole MA closed period (15 February – 15 March); a harbor 

porpoise was not taken on this haul (Table 10). 

About 60% (261 of 437) of the observed large mesh hauls had at least one gear characteristic or 

closure requirement out of compliance. In addition, 65% (28 of 43) of the harbor porpoise takes 

were in large mesh hauls that were out of compliance for at least one of the gear characteristics 

or closures requirements of the HPTRP (Table 10). 

Most of the hauls that were out of compliance were violating the string length requirement 

(Table 10). Bycatch rates increased as string length increased (Figure 10). For example, the 

bycatch rate of all large mesh hauls was 0.320 harbor porpoises per mtons landed (43 takes in 

437 hauls). In comparison, the bycatch rate of hauls that used strings less than or equal to 4,000 

ft was 0.121 harbor porpoises per mtons landed (3 takes in 139 hauls) and the rate for strings 

greater than 4,000 ft was 0.368 harbor porpoises per mtons landed (40 takes in 295 hauls). Note 

that under the HPTRP, the large mesh gillnets fishing within the Waters off New Jersey 

(excluding the Mudhole) MA may not exceed 4,800 ft. 

Other hauls that were out of compliance used smaller than required twine sizes and did not use 

tie downs (Table 10). 

3.5 Correlated Factors 

When developing a 1–factor model, three factors (bottom depth, distance to the 50 m depth 

contour and number of anchors) were equally highly significant. Thus, because the AIC values 

were so similar (a difference of about one AIC unit), it was not possible to tell which factor was 

appropriate to use as the best 1-factor model. In conclusion, three 1-factor models were expanded 

upon to develop three final models (Table 11). Two of these three final models ended up having 
23

the same factors included, just in a different order; thus, there were two unique final models. 

These two unique final models included fixed environmental factors (bottom depth and distance 

to the 50 m depth contour), varying environmental factors (surface and bottom water 

temperatures and winter NAO index value), and fishery characteristics (ship’s gross tonnage, 

anchor weight, number of anchors, and duration of time gillnet was in the water [i.e., soak 

duration]). 

For the two final unique models, Figures 11 and 12 indicate the values of each factor (x–axis) 

that were associated with a higher than average bycatch rate (y–axis value greater than zero, that 

is, above the dashed horizontal line). 

A description and interpretation of the factors follows. 

3.5.1 Fixed environmental factors

One interpretation of the fixed environmental factors (bottom depth and distance to the 50 m 

depth contour) is that these factors define the area of highest bycatch rates (inside and around 

Hudson Canyon). This area is also an area with the majority of gillnet fishing effort, as shown 

by the location of gillnet trips recorded in the vessel trip reports (VTR) during January – April, 

2004 – 2005, which are two years in the center of the study time period (Figures 13 and 14). 

3.5.2 Varying environmental factors 

One interpretation of the inclusion of the varying environmental factors (surface and bottom 

water temperatures and winter NAO index value) is that these factors explain why the bycatch 

rates varied from year to year and month to month. That is, higher than average bycatch rates 

were observed when the winter NAO index value6 was smaller (<0.25), and when the water 

temperatures were cooler than about 7°C surface temperature and 6°C bottom temperature 

(Figures 11 and 12). 

These results suggest that these environmental factors may cause the spatial/temporal 

distribution of harbor porpoises and fish (and/or fishers) to overlap more in some years (with 

small NAO index values and cooler water temperatures) than in other years (with large NAO 

index values and warmer water temperatures). However, there are not enough fishery–

independent sighting surveys in the winter in this region to fully investigate this hypothesis. 

3.5.3 Gear and fishing characteristic factors

The gear and fishing characteristics that were most highly correlated with bycatch were the 

numbers of anchors used, total weight of the anchors, soak duration, and gross tonnage of the 

vessel. 

All of the observed takes in this region were on hauls that soaked for 48 or more hours. Overall, 

63% of all observed hauls soaked for 48 or more hours, and 81% of the observed landings came 

from hauls that soaked for 48 or more hours. Half of the takes were from hauls that soaked for 

more than one week; however, only 11% of the observed hauls soaked for more than one week, 

and 15% of the observed landings were from hauls that soaked for more than one week. The 

bycatch rate from hauls that soaked for more than one week was 0.53 harbor porpoises per mtons 

 

6

 See the Appendix for the definition of the North Atlantic oscillation (NAO) index value and how it is related to 

weather conditions and marine life distribution and abundance in northwestern Atlantic waters. 
24

landed (15 takes per 28.2 mtons landed) as compared to 0.10 harbor porpoises per mtons landed 

(15 takes per 155.349 mtons landed) for hauls that soaked for less than one week. If it is 

assumed that there is a cause and effect relationship between the bycatch rate and soak duration, 

and if it is assumed the soak durations of all hauls were less than one week, it might be possible 

to reduce the observed bycatch rate by about five times. Average landings on hauls targeting 

monkfish that soaked for less than one week (0.30 mtons) were about the same for monkfish 

hauls that soaked for more than one week (0.35 mtons). 

The relationship between soak duration and the bycatch rate still held when looking only at 2006, 

the year with the most takes and a low winter NAO index value. The bycatch rate for hauls that 

soaked for less than one week was 0.31 harbor porpoises per mtons landed, and the rate for hauls 

that soaked more than one week was 0.99 harbor porpoises per mtons landed. 

Most (93%) of the observed hauls used two anchors, an additional 6% used four anchors, and a 

few hauls used one, three, or six anchors. As expected, as the number of anchors increased so 

did the total weight of the anchors. Thus, the factors number of anchors and total weight of 

anchors are correlated with each other. Bycatch rates of hauls that used four anchors (usually 88 

lbs) were 100 times larger than that of hauls that used two anchors (usually 44 lbs). For hauls 

that used four anchors, there were 11 takes in 26 hauls, which resulted in a bycatch rate of 0.423 

takes per haul. For hauls that used two anchors, there were 18 takes in 401 hauls, which resulted 

in a bycatch rate of 0.045 takes per haul. All observed hauls that used four anchors were 

targeting monkfish, though only 8.3% of the observed monkfish hauls used four anchors. It 

should not be surmised that using four anchors caused the higher bycatch. The higher bycatch 

rate could be related to the reason for using four anchors, to some other factor that happened to 

be statistically correlated with the number of anchors, or by simple chance since there were only 

26 observed hauls that used four anchors. 

To investigate possible reasons for why four anchors were used instead of the usual two anchors, 

a classification tree analysis was used to determine which fishing practices and gear 

characteristics were most common for hauls with four anchors. This analysis showed that hauls 

that used four anchors had either long soak durations (>6.5 days) or were hauled back when the 

wind speeds were fairly high (>13.5 knots) (Figure 15). The average (and median) string lengths 

were not different for strings with two versus four anchors (two anchors: mean = 4,074 ft and 

median = 4,500 ft versus four anchors: mean = 4,569 ft and median = 4,500 ft). Observed 

monkfish hauls with four anchors were on average on steeper bottom slopes (Figure 16). 

Perhaps more anchors were used when the captain knew the soak duration would be long, when 

the weather was predicted to be poor, or when the bottom slope was steep. On the other hand, 

use of four anchors could have been a personal preference since only two of the 63 observed 

vessels targeting monkfish used four anchors. Thus, it appears that numbers of anchors and 

amount of anchor weights are related to the water depth and soak duration, which were also 

related to harbor porpoise bycatch rates. High bycatch rates were probably not directly caused 

by the number of anchors (or anchor weight) but were more directly related to the reasons for 

their use: location (water depth and bottom slope) and soak duration. 

All of the takes were from vessels that were either small, less than or equal to 20 tons (10 takes 

from 67 hauls), or from vessels that did not have the tonnage reported (33 takes from 300 hauls). 

Until the tonnage of all the vessels is identified, this factor does not provide much information 

about which fishery characteristics were related to the bycatch rate. 
25

Table 6. Descriptive statistics about the bycatch of harbor porpoises (Phocoena phocoena) in the 

New Jersey region in January – April, 1999–2007.

Year 

 1999 2000 2001 2002 2003 2004 2005 2006 2007 Total 

Number of observed 

hauls 186 16 26 7 20 66 84 201 115 721

Number of observed 

trips 61 3 8 2 8 18 27 54 21 202

Number of observed 

vessels 26 3 4 1 5 14 17 32 17 119

Number of observed 

hauls with one or 

more take 0 0 0 0 1 0 7 22 0 30

Total number of 

observed takes 0 0 0 0 1 0 15 27 0 43

Bycatch rate 

(observed 

takes/observed 

number of hauls) 0 0 0 0 0.050 0 0.179 0.134 0 0.060

Bycatch rate 

(observed 

takes/observed mtons 

landed) 0 0 0 0 0.110 0 0.445 0.530 0 0.233

Table 7. For each month, the number of observed hauls and takes of harbor porpoises (Phocoena 

phocoena) and resulting bycatch rates in the New Jersey region. 

Month 

 Jan Feb Mar Apr 

Number of observed hauls 328 114 46 233 

Number of observed takes 12 28 0 3 

Bycatch rate (observed 

takes/observed hauls) 0.037 0.246 0 0.013 

Bycatch rate (observed 

takes/observed mtons landed) 0.109 0.775 0 0.105 
26

Table 8. For the New Jersey region, observed bycatch rates (Byc Rate) of harbor porpoises 

(Phocoena phocoena) and numbers of observed hauls (Num Obs) for various gear characteristics, 

fishing practices, and environmental factors. The bycatch rate was defined as observed number 

of hauls with one or more takes per the observed mtons landed. The overall average bycatch rate 

was 0.163 harbor porpoises per mtons landed. 

Categories of factors with ** in the Num Obs column had less than 6 mtons landed (thus given the 

overall bycatch rate for this region, there was a very small chance of observing a take). 

Categories of factors with * in the Num Obs column had less than 12 mtons landed (thus, there 

was a small chance of observing a take). 

High bycatch rates (≥ 0.3 harbor porpoises per mtons landed) are highlighted. 

Data were collected from January – April, 1999 –2007. 

Category 

Num 

Obs 

Byc 

Rate Category 

Num 

Obs 

Byc 

Rate Category 

 Num 

Obs 

Byc 

Rate 

MONTH TARGET SPECIES LENGTH OF STRING (ft) 

Jan 328 0.109 

Leptoscopus 

americanus 430 0.225 0–2,000 235 0 

Feb 114 0.443 Pomatomus saltatrix 20** 0 2,000–4,000 174 0.056 

Mar 46* 0 Clupea harengus 2** 0 4,000–6,000 213 0.393 

Apr 233 0.070 Scomber scombrus 37* 0 6,000–8,000 74 0.025 

 Brevoortia tyrannus 9** 0 8,000–14,000 11** 0.184 

YEAR Cynoscion regalis 81** 0 

1999 186 0 Alosa sapidissima 47** 0 HANGING RATIO 

2000 16** 0 Mustelus, Squalus 41 0 0.33 61 0.080 

2001 26** 0 Rajidae 4** 0 0.5 648 0.172 

2002 7** 0 Leucoraja ocellata 3** 0 

2003 20* 0.110 Morone saxatilis 24** 0 TWINE SIZE (mm) 

2004 66 0 Groundfish 21** 0 0.33 7** 0 

2005 84 0.208 Scombridae 2** 0 0.4 5** 0 

2006 201 0.432 0.47 1** 0 

2007 115* 0 SURFACE TEMPERATURE (°C) 0.52 19** 0 

 2–4 11** 0.524 0.57 41* 0 

BIOLOGICAL SAMPLING? 4–6 199 0.104 0.62 12** 0 

yes 146 0.140 6–8 216 0.284 0.66 18** 0 

no 575 0.170 8–10 155 0.066 0.7 45 0 

 10–12 17** 0 0.74 9** 0 

STEAM TIME (hrs) 0.81 60 0.054 

0–2 377 0.033 BOTTOM TEMPERATURE (°C) 0.9 375 0.244 

2–4 185 0.310 3–4 12** 0 

4–6 99 0.200 4–5 115 0.175 MESH SIZE (in) 

6–8 38 0.053 5–6 171 0.257 2–4 70 0 

8–10 19* 0.213 6–7 139 0.177 4–6 186 0 

10–14 2** 0 7–8 74 0.181 6–8 27* 0 

 8–9 44 0 8–10 3** 0 

WIND SPEED (kts) 9–10 8** 0 10–12 434 0.224 

0–10 413 0.171 

10–20 256 0.181 SOAK DURATION (hrs) USED TIE DOWNS? 

20–30 27* 0 0–100 540 0.051 no 300 0 

30–40 3** 0 100-200 141 0.287 yes 407 0.241 

 200-700 39** 0.591 unknown 14** 0 
27

Table 8 (cont). For the New Jersey region, observed bycatch rates (Byc Rate) of harbor porpoises 

(Phocoena phocoena) and numbers of observed hauls (Num Obs) for various gear characteristics, 

fishing practices, and environmental factors. The bycatch rate was defined as observed number 

of hauls with one or more takes per the observed mtons landed. The overall average bycatch rate 

was 0.163 harbor porpoises per mtons landed. 

Categories of factors with ** in the Num Obs column had less than 6 mtons landed (thus given the 

overall bycatch rate for this region, there was a very small chance of observing a take). 

Categories of factors with * in the Num Obs column had less than 12 mtons landed (thus, there 

was a small chance of observing a take). 

High bycatch rates (≥ 0.3 harbor porpoises per mtons landed) are highlighted. 

Data were collected from January – April, 1999 –2007. 

Category 

Num 

Obs 

Byc 

Rate Category 

Num 

Obs Byc Rate Category 

Num 

Obs 

Byc 

Rate 

AMOUNT DISCARD (lbs) NET HEIGHT (ft) USED ANCHORS? 

0–200 120 0.103 0–5 23 0 no 77** 0 

200–400 14* 0.185 5–10 312 0.110 yes 644 0.165 

400–1,400 8** 0 10–15 221 0.280 

 15–30 91* 0 

LENGTH OF TIE DOWN (ft) NUMBER OF SPACES USED ADDED WEIGHTS? 

2–3 216 0.123 0–10 76 0 no 453 0 

3–4 144 0.405 10–20 75 0.042 yes 66* 0.238 

4–5 4** 0 20–40 11* 0 unknown 198 0.166 

5–6 8** 0 30–40 1** 0 

 ANCHOR WEIGHT TYPE 

NUMBER OF ANCHORS ANCHOR WEIGHT (lbs) Unknown 80** 0 

1 1** 0 0–20 2** 0 Danforth-type 278 0.064 

2 401 0.166 20–40 89 0.163 Dead weight 363 0.275 

3 1** 0 40–60 424 0.114 

4 26 1.070 60–80 39** 0 DEPTH OF LEADLINE (fm) 

6 4** 0 80–100 40 0.925 0–10 194 0 

 100–160 41** 0 10–20 132 0.134 

VESSEL GROSS TONS 20–30 95 0.132 

0–20 80 0.365 AMOUNT LANDED (mtons) 30–40 61 0.438 

20–40 84 0 0–0.5 602 0.227 40–50 22* 0.715 

40–60 23** 0 0.5–1 82 0.125 50–60 8** 0 

60–120 20* 0 1–1.5 15 0 

 1.5–3 7 0.071 
28

Table 8 (cont). For the New Jersey region, observed bycatch rates (Byc Rate) of harbor porpoises 

(Phocoena phocoena) and numbers of observed hauls (Num Obs) for various gear characteristics, 

fishing practices, and environmental factors. The bycatch rate was defined as observed number 

of hauls with one or more takes per the observed mtons landed. The overall average bycatch rate 

was 0.163 harbor porpoises per mtons landed. 

Categories of factors with ** in the Num Obs column had less than 6 mtons landed (thus given the 

overall bycatch rate for this region, there was a very small chance of observing a take). 

Categories of factors with * in the Num Obs column had less than 12 mtons landed (thus, there 

was a small chance of observing a take). 

High bycatch rates (≥ 0.3 harbor porpoises per mtons landed) are highlighted. 

Data were collected from January – April, 1999 –2007. 

Category 

Num 

Obs 

Byc 

Rate Category 

Num 

Obs Byc Rate Category 

Num 

Obs 

Byc 

Rate 

SEDIMENT TYPE 

WINTER NORTH ATLANTIC 

OSCILLATION INDEX

CHLOROPHYLL α

CONCENTATION (mg/m3) 

Clay – 

Silt/Sand 105 0.295 –0.4 – –0.2 227 0.396 0–10 210 0.422 

Gravel 24 0 –0.2 – 0.0 0 0 10–20 35** 0 

Gravel – Sand 97 0.078 0.0 – 0.2 20** 0.11 20–30 3** 0 

Sand 367 0.174 0.2 – 0.4 157 0.133 30–60 3** 0 

Sand – 

Clay/Silt 5 0 0.4 – 0.6 186 0 

 0.6 – 1.2 16** 0 

LOG10(CHLOROPHYLL α) [log10

(mg/m3

)] 

DISTANCE TO 50 M DEPTH 

CONTOUR (m) –0.5 – 0 17** 0.52 

0–2,000 83 0.28 

NORTH ATLANTIC OSCILLATION 

INDEX 0–0.5 86 0.331 

2,000–4,000 73 0.498 –1 – –0.5 83 0.318 0.5–1 107 0.556 

4,000–6,000 45 0.325 –0.5 – 0 88 0.215 1–1.5 38** 0 

6,000–8,000 42 0.366 0 – 0.5 77 0 1.5–2 3** 0 

>8,000 356 0 0.5 – 1.0 99 0.033 

 1.0 – 1.5 198 0.33 DEPTH OF FLOATLINE (fm) 

 1.5 – 2.0 61 0.043 0–20 238 0 

 20–40 243 0.061 

40–60 145 0.091 

 60–100 91 0.611 
29

Table 9. From January – April, 1999–2007, the numbers of observed hauls and takes of harbor 

porpoises (Phocoena phocoena) that were in gillnets in the New Jersey region which were in and 

out of compliance with the harbor porpoise take reduction plan (HPTRP). Note any one haul could 

have been out of compliance for one or more of the requirements. 

Large mesh is 7–18 in; small mesh is >5–<7 in; very small mesh (not regulated in HPTRP) is ≤5 in.

ALL HAULS 

In 

compliance? 1999 2000 2001 2002 2003 2004 2005 2006 2007 Total

No 25 0 9 7 19 43 63 115 11 292

Yes 161 16 17 0 1 23 21 86 104 429

% 

Number of compliant 87 100 65 0 5 35 25 43 90 60

hauls TOTAL 186 16 26 7 20 66 84 201 115 721

No 0 0 0 0 1 0 9 18 0 28

Number of Yes 0 0 0 0 0 0 6 9 0 15

takes TOTAL 0 0 0 0 1 0 15 27 0 43

 

SMALL 

MESH 

In 

compliance? 1999 2000 2001 2002 2003 2004 2005 2006 2007 Total

No 15 0 0 0 0 15 0 1 0 31

Yes 28 0 0 0 0 1 0 25 48 102

% 

Number of compliant 65 0 0 0 0 6 0 96 100 77

hauls TOTAL 43 0 0 0 0 16 0 26 48 133

No 0 0 0 0 0 0 0 0 0 0

Number of Yes 0 0 0 0 0 0 0 0 0 0

takes TOTAL 0 0 0 0 0 0 0 0 0 0

 

LARGE 

MESH 

In 

compliance? 1999 2000 2001 2002 2003 2004 2005 2006 2007 Total

No 10 0 9 7 19 28 63 114 11 261

Yes 89 7 4 0 1 5 21 32 17 176

% 

Number of compliant 90 100 31 0 5 15 25 22 61 40

hauls TOTAL 99 7 13 7 20 33 84 146 28 437

No 0 0 0 0 1 0 9 18 0 28

Number of Yes 0 0 0 0 0 0 6 9 0 15

takes TOTAL 0 0 0 0 1 0 15 27 0 43

 

VERY 

SMALL 

Not 

regulated 1999 2000 2001 2002 2003 2004 2005 2006 2007 Total

Number of 

hauls 

Not 

regulated 44 9 13 0 0 17 0 29 39 151

Number of 

takes 

Not 

regulated 0 0 0 0 0 0 0 0 0 0
30

Table 10. From January – April, 1999–2007, the numbers of observed hauls and harbor porpoises 

(Phocoena phocoena) takes (HP) in large mesh gillnets in the New Jersey region which were in 

and out of compliance with the harbor porpoise take reduction plan (HPTRP), as applied to (A) the 

Mudhole management area (MA), and (B) the Waters off New Jersey (excluding the Mudhole) MA, 

and (C) all of the New Jersey region (A+B). Note, any one haul could have been out of compliance 

for one or more of the requirements.

(A) MUDHOLE MA

 

FLOATLINE LENGTH GREATER THAN 3,900 FT 

 1999 2000 2001 2002 2003 2004 2005 2006 2007 Total

Number of hauls 0 0 0 7 2 0 15 34 4 62

Number of trips 0 0 0 2 1 0 6 12 2 23

Number of 

vessels 0 0 0 1 1 0 4 9 2 17

Number of HP 

takes 0 0 0 0 0 0 1 3 0 4

 

HAULED GILLNETS DURING THE CLOSED PERIOD: 15 FEB – 15 MAR 

 1999 2000 2001 2002 2003 2004 2005 2006 2007 Total

Number of hauls 0 0 0 0 0 0 0 0 1 1

Number of trips 0 0 0 0 0 0 0 0 1 1

Number of 

vessels 0 0 0 0 0 0 0 0 1 1

Number of HP 

takes 0 0 0 0 0 0 0 0 0 0

 

(B) WATERS OFF NEW JERSEY (EXCLUDING THE MUDHOLE) MA

 

FLOATLINE LENGTH GREATER THAN 4,800 FT 

 1999 2000 2001 2002 2003 2004 2005 2006 2007 Total

Number of hauls 7 0 6 0 17 24 37 65 7 163

Number of trips 5 0 4 0 7 9 16 26 3 70

Number of 

vessels 5 0 3 0 4 7 12 16 3 50

Number of HP 

takes 0 0 0 0 1 0 8 14 0 23
31

Table 10 (cont.). From January – April, 1999–2007, the numbers of observed hauls and harbor 

porpoises (Phocoena phocoena) takes (HP) in large mesh gillnets in the New Jersey region which 

were in and out of compliance with the harbor porpoise take reduction plan (HPTRP), as applied to 

(A) the Mudhole management area (MA), and (B) the Waters off New Jersey (excluding the 

Mudhole) MA, and (C) all of the New Jersey region (A+B). Note, any one haul could have been out 

of compliance for one or more of the requirements.

(C ) ENTIRE NEW JERSEY REGION: MUDHOLE MA AND WATERS OFF OF 

NEW JERSEY (EXCLUDING THE MUDHOLE) MA

 

TWINE SIZE LESS THAN 0.90 MM 

 1999 2000 2001 2002 2003 2004 2005 2006 2007 Total

Number of hauls 0 0 0 0 0 12 16 20 0 48

Number of trips 0 0 0 0 0 4 7 5 0 16

Number of 

vessels 0 0 0 0 0 4 5 4 0 13

Number of HP 

takes 0 0 0 0 0 0 0 1 0 1

 

TIED DOWNS NOT USED 

 1999 2000 2001 2002 2003 2004 2005 2006 2007 Total

Number of hauls 3 0 0 0 0 3 11 0 6 23

Number of trips 1 0 0 0 0 1 4 0 2 8

Number of 

vessels 1 0 0 0 0 1 1 0 2 5

Number of HP 

takes 0 0 0 0 0 0 0 0 0 0

 

HAULED NETS DURING THE CLOSED PERIOD 1–20 APRIL 

 1999 2000 2001 2002 2003 2004 2005 2006 2007 Total

Number of hauls 0 0 3 0 0 0 0 3 0 6

Number of trips 0 0 1 0 0 0 0 2 0 3

Number of 

vessels 0 0 1 0 0 0 0 1 0 2

Number of HP 

takes 0 0 0 0 0 0 0 3 0 3
32

Table 11. Final models of the bycatch rates of harbor porpoises (Phocoena phocoena) in the New 

Jersey region when starting with three different 1-factor models (A-C). The last column is the 

difference in the Akaike Information Criterion (AIC) from the row above; the larger the difference, 

the more that factor contributed to explaining the bycatch rate patterns. The lower the AIC, the 

better the model fits.

(A) Starting variable: Bottom depth 

Model 

number Factors AIC 

Difference 

from 

above 

1 None 249 0 

2 Bottom depth 186 63 

3 Above + Surface water temperature 159 27 

4 Above + Winter North Atlantic oscillation index 136 23 

5 Above + Distance to 50 m depth contour 128 8 

6 Above + Vessel gross tons 121 7 

7 Above + Anchor weight 119 2 

(B) Starting variable: Distance to 50 m depth contour 

Model 

number Factors AIC 

Difference 

from 

above 

1 None 249 0 

2 Distance to 50 m depth contour 185 64 

3 Above + Number of anchors 152 33 

4 Above + Bottom water temperature 138 14 

5 Above + Winter North Atlantic oscillation index 130 8 

6 Above + Vessel gross tons 121 9 

7 Above + Soak duration 119 2 

(C) Starting variable: Number of anchors 

Model 

number Factors AIC 

Difference 

from 

above 

1 None 249 0 

2 Number of anchors 187 62 

3 Above + Distance to 50 m depth contour 152 35 

4 Above + Bottom water temperature 138 14 

5 Above + Winter North Atlantic oscillation index 130 8 

6 Above + Vessel gross tons 121 9 

7 Above + Soak duration 119 2 
33

January

February

March

April

May

June

July

August

September

October

November

Decembe

month

0

20406080

100120140160 1999

20002001200220032004200520062007average

Number of observed hauls

Figure 7. By year, numbers of observed hauls in the New Jersey region, 1 January 1999 – 31 May 2007. 
34

Figure 8. Locations of observed hauls by year (colored circles) and observed hauls with harbor porpoise (Phoc

(white crosses) in the New Jersey region, which includes the Mudhole management area (MA), Waters off New 

Mudhole) MA, and Hudson Canyon. Data are from January – April, 1999–2007. Depth contours are 10, 30, 40, 50, 1
35

Figure 9. Locations of observed hauls without harbor porpoise (Phocoena phocoena) takes (black dashes) and takes, where the numbers of takes per haul is identified. Size of stack indicates number of takes: dash repre

stack represents four animals per haul. Data from the New Jersey region, which include the Mudhole managemenNew Jersey (excluding the Mudhole) MA, and Hudson Canyon and are from January – April, 1999–2007. Depth c

40, 50, 100, and 200 m. 
36

0 2000 4000 6000 8000

Total gear length (ft)

-4 -2 0

relative bycatch rate best estimate

1

SE confidence

limit

1 SE confidence limit

reference line

reference line

Figure 10. Relationship between the relative harbor porpoise (Phocoena phocoena) bycatch rate (y-axis) and toaxis) using data from the New Jersey region, collected January – April, 1999–2007. This plot shows that hauls 

average bycatch rates are hauls with total gear lengths greater than about 4,000 ft. Tick marks on the x–axis indobservations, and the tick marks are jittered (spread out) to help display where there are values that are shared bThe solid black line represents the overall pattern of these many observations and indicates the best estimate of tgiven total gear length. Dotted lines are the upper and lower one standard error (SE) confidence limits about the 

red reference line indicates the average relative bycatch rate (y = 0), and values along the y axis indicate the difaverage. Values above the red line have higher than average bycatch rates, and those below have a lower than The blue reference line indicates the total gear length with the average bycatch rate (less than 4,000).
37

0 50 100 

Anchor weight (lbs)

-1 0 1 2 3

relative bycatch rate 0 20 40 60 80 100 120

Vesel gross tonnage

-40-30-20-10 0

relative bycatch rate

0 20000 40000 60000 80000 100

Distance to 50m depth cont

-120 -80 -40 0

relative bycatch rate 0.0 0.5 1.0

Winter North Atlantic oscillation index

-50 -30 -10

relative bycatch rate

4 6 8

Sea surface temperature 

-3 -2 -1 0 1 2 3

relative bycatch rate -80 -60 -40 -20 0

Bottom depth (fa)

-3 -2 -1 0 1

relative bycatch rate

Figure 11. Results of stepwise analysis to model harbor porpoise (Phocoena phocoena) bycatch rates in the New the first factor in the model was bottom depth (fa). Tick marks on the x–axis indicate the values of the observation

are jittered (spread out) to help display where there are values that are shared by many observations. The solid blaoverall pattern of these many observations and indicates the best estimate of the bycatch rate at any given value 

The dashed horizontal line indicates the average relative bycatch rate (y = 0), and values along the y axis indicate to this average. Values above this line have higher than average bycatch rates, and those below have a lower than 
38

0 20000 40000 60000 80000 100000120000 140000

distance to the 50m depth contour (m)

-120 -80 -40 0

relative bycatch rate 2345

Number of anchors

-2 -1 0 1

relative bycatch rate

4 5 6 7 8 9 10

Bottom water temperature (C)

-3 -2 -1 0 1 2

relative bycatch rate 0.0 0.5 

Winter North Atlantic oscillation 

-40-30-20-10 0

relative bycatch rate

0 20 40 60 80 100 120

Vessel gross tonnage

-40-30-20-10 0

relative bycatch rate 0 100 200 

Soak duration (hrs)

0.0 0.5 1.0 1.5

relative bycatch rate

Figure 12. Results of stepwise analysis to model harbor porpoise (Phocoena phocoena) bycatch rates in the New the first factor in the model was distance to the 50 m depth contour (m). Tick marks on the x–axis indicobservations, and the tick marks are jittered (spread out) to help display where there are values that are shared bThe solid black line represents the overall pattern of these many observations and indicates the best estimate of tgiven value of the x-axis variable. The dashed horizontal line indicates the average relative bycatch rate (y = 0), aaxis indicate the difference relative to this average. Values above this line have higher than average bycatch rhave a lower than average bycatch rate.
39

Figure 13. Locations of gillnet trips within the New Jersey region, which includes the Mudhole management area 

Jersey (excluding the Mudhole) MA, and Hudson Canyon during January and February in 2004 and 2005, accordin

reports (VTR). Depth contours are 10, 30, 40, 50, 100, and 200 m.
40

Figure 14. Locations of gillnet trips within the New Jersey region, which includes the Mudhole management area 

Jersey (excluding the Mudhole) MA, and the Hudson Canyon during March and April in 2004 and 2005, accordin

reports (VTR). Depth contours are 10, 30, 40, 50, 100, and 200 m.
41

Figure 15. Using data collected from the gillnet fisheries in the New Jersey region from January – 

April in 1999–2007, a classification tree model was used to predict the number of anchors that 

were used: two versus four (ignoring the few hauls that used one, three or six anchors). To 

interpret a classification tree, each factor is in a different colored box. The top break means hauls 

that were in waters less than 59.4 fa had characteristics that are in the left branch, and hauls in 

deeper water (in the right branch) used two anchors. The predicted number of anchors (two or 

four) is the value at the end of each branch in yellow shaded boxes.
42

Figure 16. Locations of observed hauls with harbor porpoise (Phocoena phocoena) takes (yellow 

crosses) and observed hauls (colored circles) with various numbers of anchors (A) and weights of 

the anchors (B) in the New Jersey region, which includes the Mudhole management area (MA), 

Waters off New Jersey (excluding the Mudhole) MA, and Hudson Canyon. Data are from January – 

April, 1999 – 2007. Depth contours are 10, 30, 40, 50, 100, and 200 m.

(A) 

(B) 
43

4. CAPE COD REGION

4.1 Summary 

The Cape Cod region (Figure 1) is the southern portion of the Northeast gillnet fishery, which 

includes the Cape Cod South HPTRP management area and is located south of Massachusetts 

and Rhode Island, north of the 39o 30’N latitude line and east of the 72° 30’W longitude line. 

Harbor porpoise bycatch rates in the Cape Cod region have been consistently high since 2000, 

and they were particularly high in 2005–2007. 

Since the implementation of the HPTRP, the NEFOP observed 2,831 hauls in the Cape Cod 

region, in which 87 harbor porpoise takes were observed. Of these takes, 24 were inside the 

Cape Cod South MA, as defined in the HPTRP, and 63 were outside this management area. All 

observed harbor porpoise takes occurred from December – May and were in gillnets targeting 

either monkfish or winter skate (Leucoraja ocellata). 

The bycatch rate of hauls outside the Cape Cod South MA (where pingers are not required) was 

about 50% higher than the bycatch rate within the Cape Cod South MA (where pingers are 

required): 0.102 versus 0.066 harbor porpoises per mton landed, respectively. Regardless of 

whether a haul was from inside or outside of the Cape Cod South MA, bycatch rates of hauls that 

used pingers (1,055 hauls) were about half that of hauls that did not use pingers (1,776 hauls): 

0.053 versus 0.098 harbor porpoises per mtons landed, respectively. 

Since January 1999, three observed hauls (from one trip) were inside the Cape Cod South MA 

during March, the month closed to all gillnetting. Of the 1,665 observed hauls in the Cape Cod 

South MA during the time period pingers were required, 45% used the required number of 

pingers, an additional 40% did not use any pingers, while the remaining 15% used some pingers 

but fewer than the required number of pingers. 

A statistical model that best predicted the bycatch rates in this region included the following 

factors (in order of importance): steam time, day of the year, twine size, and temporary home 

state. This bycatch rate model identified several issues related to high bycatch. First, the 

bycatch rate for a twine size of 0.33 mm in strings targeting monkfish (mesh sizes ≥ 10 in) was 

extremely high; however, the normal practice was to use twine sizes ≥ 0.57mm. Second, the 

highest bycatch rates were February – April, with lower rates in the surrounding months of 

December, January, and May, all of which are the times that are managed under the HPTRP. 

Third, most of the observed takes were in a region where pingers were not required; that is, the 

region from the southern boundary of the Cape Cod South MA (40o 40’N latitude) to the 40oN 

latitude line, and then east to the 70oW longitude line. 

4.2 Observer Coverage 

In the Cape Cod region (Figure 1) from 1 January 1999 – 31 May 2007, the numbers of observed 

hauls per month/year ranged from 0–298 hauls per month, with an average of about 46 hauls per 

month, and the most observed hauls were in May (Figure 17). All observed harbor porpoises in 

this region were taken December – May, the same time period this area is managed by the 

HPTRP. Thus, further analyses focused on hauls observed in the Cape Cod region from January 

– May in 1999–2007 and December in 1999–2006. 

In this region and time period, there were 2,831 hauls observed, which were from 659 trips and 

312 vessel-years, which included 132 unique vessels. There were 123–499 hauls observed per 
44

year, which were from 32–124 trips per year, and from 15–69 vessels per year (Table 12). The 

observed hauls in December and January were generally closer to shore than those observed in 

other months, February – May (Figure 18). The distributions of observed hauls from each year 

appear to span the same general fishing areas, though the observed hauls in more recent years 

(since 2004) appear to be located more offshore: south of the Cape Cod South MA towards the 

200 m depth contour (Figure 19). 

4.3 General Bycatch Patterns 

Bycatch rates in this region increased over the years, where the bycatch rates from 2007 (January 

– May) were the highest (Table 12). Harbor porpoises were taken inside and outside of the Cape 

Cod South MA in many of the years since the implementation of the HPTRP (Figure 20). Of the 

2,831 hauls observed in this region, 2,761 hauls did not have any harbor porpoise bycatch, 57 

hauls had 1 take, 9 hauls had 2 takes, and 4 hauls had 3 harbor porpoise takes. Hauls that took 

more than one harbor porpoise appear to have been slightly more concentrated in or near the 

southern border of the Cape Cod South MA (Figure 21). Bycatch rates were highest in February 

– May and lowest in December (Table 13). 

The bycatch rate of hauls outside the Cape Cod South MA (which were not required to use 

pingers) was about 50% greater than the bycatch rate of hauls within the Cape Cod South MA 

(which were required to use pingers): 0.102 versus 0.066 harbor porpoises per mtons landed, 

respectively (Table 14). 

Regardless of whether a haul was inside or outside of the management area, the bycatch rate of 

hauls that used pingers (1,055 hauls) was about half that of hauls that did not use pingers (1,776 

hauls): 0.053 versus 0.098 harbor porpoises per mtons landed, respectively (Table 14). 

Bycatch rates (sum of observed takes per sum of observed mtons landed) for categorizations of 

many factors are listed in Table 14. Categories with high bycatch rates included: hauls without 

pingers, hauls outside of the Cape Cod South MA, the years of 2006 (January – May plus 

December) and 2007 (January – May), the months of February and April, hauls that targeted 

monkfish and winter skate, waters that were 50–100 fa deep, surface water temperatures of 4–

6oC and bottom water temperatures of 4–8oC, long soak durations (>200 hrs), long strings 

(>4,000 ft), hang ratio of 0.5, mesh sizes of 10–12 in, gillnet heights of 10–15 ft, leadline depths 

of 25–50 fa (net may not be touching the bottom), hauls that used additional weights, small or 

large NAO index values, steam times of 5–10 hrs from the ship’s temporary home port, and 

hauls where the observer did not conduct biological fish sampling but did concentrate watching 

the gillnet while it was being hauled in to make a special effort to document all incidental takes, 

particularly those that might fall from the net before it reaches the ship’s deck. 

4.4 Compliance 

Since the implementation of the HPTRP, there were 2,831 hauls observed in the Cape Cod 

region, of which 1,665 hauls were inside the Cape Cod South MA. Only three observed hauls 

(from one trip) were inside the management area during March, the month closed to all 

gillnetting. The log from this trip stated that the nets were set on 1 March 2007 and hauled back 

on 4 March 2007. Locations of these hauls were close to the southern border of the Cape Cod 

South MA. These three strings were each 20 panels long, had 20 pingers/string (1 short of the 

required number), and had no harbor porpoise bycatch. 
45

In the Cape Cod South MA, during January, February, April, May, and December (months 

pingers are required), about 40% (657 hauls) of the observed hauls did not use any pingers. 

These 657 observed hauls were from 185 trips and 53 different vessels, which were from 

Massachusetts, New York, and Rhode Island. These 657 hauls took 13 harbor porpoises in 12 

hauls, 8 trips, and 7 vessels. The 12 hauls with takes occurred in 2003 (1 haul), 2004 (4 hauls), 

2006 (4 hauls), and 2007 (3 hauls), and were in January (2 hauls), April (1 haul), May (8 hauls), 

and December (1 haul). 

In contrast, there were 47 observed hauls (13 trips and 8 vessels) that were outside of the Cape 

Cod South MA and used pingers, even though pingers were not required. These hauls had no 

harbor porpoise takes and were observed in various years: 1 haul in 2001, 3 in 2002, 27 in 2003, 

7 in 2005, and 9 in 2007. 

Assuming compliance with the pinger requirements means 90% or more of the required number 

of pingers were on the net when it was hauled in (thus, allowing for the possibility that the 

commonly used 10-net string is missing one pinger, which could have fallen off accidently 

during the time the net was in the water), then of the 1,665 observed hauls in the Cape Cod South 

MA during the time period pingers were required, 47% used 90% or more of the required 

pingers, an additional 40% did not use any pingers, while the remaining 13% used some pingers 

but less than 90% of the required number. If it is assumed that compliance with the pinger 

requirement means 100% of the required number of pingers were on the net when it was hauled 

back, then of the 1,665 observed hauls in the Cape Cod South MA during the time period pingers 

were required, 45% used the required number of pingers, an additional 40% did not use any 

pingers, while the remaining 15% used some pingers but less than the required number of 

pingers. 

The levels of compliance to the pinger usage management regulations and effectiveness of the 

pingers were discussed in detail in Palka et al. (2008). 

4.5 Correlated Factors 

The model that best predicted bycatch rates from this area included the following factors (in 

order of importance): steam time, day of the year, twine size, and temporary home state (Table 

15). Figure 22 indicates the values of each factor (x–axis) that had higher than average bycatch 

rates, where a value on the y–axis value that is greater than zero (above the dashed horizontal 

line) has a higher than average bycatch rate. A description and discussion about the factors 

follows. 

Steam time was the factor most highly correlated with bycatch rates. This factor appears to 

indicate the area with high bycatch rates. The range of steam times that had the highest bycatch 

rate was 4.6–9.4 hrs (Figure 22). Mapping the location of observed hauls by steam time 

indicates that the area with the highest bycatch rate (area with steam times of 4.6–9.4 hrs) was 

the area south of the Cape Cod South MA: from the southern boundary of the management area 

south to about the 40oN latitude line (Figure 23). 

The second most highly correlated factor was day of the year. The bycatch was highest February 

– April (Figure 22), as was mentioned above (Table 13). 

The next factor added to the model was twine size. Twine sizes less than 0.5 mm had the highest 

bycatch rate, and large twine sizes (≥0.74 mm) had the second highest bycatch rate (Figure 22 

and Table 14). There were nine observed hauls that used 0.33 mm twine size, of which five had 
46

a total of 11 incidentally taken harbor porpoises. These five hauls were from a single trip that 

targeted monkfish using long strings (6,000 ft) that soaked for a long time (72 or 144 hrs/string). 

Using small twine sizes when targeting monkfish does not appear to have been typical; about 

1.5% of the observed hauls that targeted monkfish used twine sizes less than 0.57 mm. Three of 

the five hauls with takes were inside the Cape Cod South MA and used 20 gillnet panels and 19 

pingers (two pingers short of the HPTRP requirements). The other two hauls with takes were 

outside of the Cape Cod South MA and did not use pingers. In conclusion, the model appears to 

have used the twine size factor to identify two issues. First, five hauls with bycatch used strings 

which do not appear to have been typical fishing gear to target monkfish. Second, high bycatch 

rates were identified in gillnets that used large twine sizes, which were the commonly used twine 

sizes in this region. It is also noted that there were several other characteristics related to hauls 

with high bycatch, such as long string lengths and long soak durations. 

The last factor added to the model was temporary home state (Table 15; Figure 22). By mapping 

the location of the hauls by their temporary home state (Figure 24), it appears that this factor has 

refined the definition of areas with high bycatch. For example, within the area of steam times of 

4.6 – 9.4 hrs (Figure 23), the highest bycatch rates were from vessels from New York (Figure 

22), which were west of the 71o30’W longitude line (Figure 25 in pink circle), and the bycatch 

rates of vessels from Massachusetts were slightly lower (though still over the average bycatch 

rate), and they were located east of the 71oW longitude line (Figure 25 in black circle). 

In conclusion, this bycatch rate model identified several issues related to high bycatch in the 

Cape Cod region. First, the bycatch rate for twine sizes of 0.33 mm in strings targeting monkfish 

(mesh sizes ≥ 10 in) was extremely high; however, the normal practice was to use twine sizes ≥

0.57 mm. Second, highest bycatch rates were in February – April, with less in the surrounding 

months of December, January, and May, thus, encompassing the present managed times in the 

HPTRP. Finally, most of the observed takes were in a region where pingers were not required; 

that is, the area from the southern boundary of the Cape Cod South MA to the 40oN latitude line 

and to the 70oW longitude line. 
47

Table 12. Descriptive statistics about bycatch of harbor porpoises (Phocoena phocoena) in the 

Cape Cod region, during January – May, 1999–2007 and during December 1999–2006.

Year 

 1999 2000 2001 2002 2003 2004 2005 2006 2007* Total

Number of observed 

hauls 292 346 123 157 145 499 369 450 450 2831

Number of observed trips 56 70 32 46 32 99 78 122 124 659

Number of observed 

vessels 17 15 16 15 22 53 39 69 66 312

Number of observed 

hauls with one or more 

take 1 5 0 2 3 12 11 13 23 70

Total number of 

observed takes 1 5 0 3 3 13 12 18 32 87

Bycatch rate (observed 

takes/observed number 

of hauls) 0.003 0.015 0 0.019 0.021 0.026 0.033 0.040 0.071 0.031

Bycatch rate (observed 

takes/observed mtons 

landed) 0.028 0.092 0 0.081 0.046 0.058 0.095 0.119 0.124 0.089

* 2007 data were from 1 January – 31 May; other years included data from January – May and 

December. 

Table 13. By month, numbers of observed hauls and takes of harbor porpoises (Phocoena 

phocoena) with the resulting bycatch rates. Data were from the Cape Cod region, January – May 

1999–2007, and December 1999–2006. 

Month 

 Jan Feb Mar Apr May Dec*

Number of observed hauls 257 290 158 573 1191 362

Number of observed takes 3 17 7 34 25 1

Bycatch rate (observed 

takes/observed hauls) 0.012 0.059 0.044 0.059 0.021 0.003

Bycatch rate (observed 

takes/observed mtons 

landed) 0.044 0.160 0.065 0.145 0.068 0.011

* 2007 data were from 1 January – 31 May; other years included data from January – May and 

December. 
48

Table 14. For the Cape Cod region, observed bycatch rates (Byc Rate) of harbor porpoises 

(Phocoena phocoena) and numbers of observed hauls (Num Obs) for various gear characteristics, 

fishing practices, and environmental factors. The bycatch rate was defined as observed number 

of takes per the observed mtons landed. The overall average bycatch rate was 0.089 harbor 

porpoises per mtons landed. 

Categories of factors with * in the Num Obs column had less than 11 mtons landed (thus given the 

overall bycatch rate for this region, there was a small chance of observing a take). 

High bycatch rates (≥ 0.1 harbor porpoises per mtons landed) are highlighted. 

Data were collected from January – May, 1999 – 2007, and December 1999 – 2006. 

Categories 

Num 

Obs 

Byc 

Rate Categories 

Num 

Obs 

Byc 

Rate Categories 

Num 

Obs 

Byc 

Rate 

MONTH TARGET SPECIES LENGTH OF STRING (ft) 

Jan 257 0.044 

Leptoscopus 

americanus 2,107 0.097 0-2000 517 0.047 

Feb 290 0.160 Pomatomus saltatrix 8* 0 2000-4000 1,224 0.060 

Mar 158 0.065 Gadus morhua 170 0 4000-6000 805 0.122 

Apr 573 0.145 

Pleuronectes 

americanus 55* 0 6000-8000 206 0.071 

May 1,191 0.068 Paralichthys dentatus 275 0 8000-14000 60 0.081 

Dec 362 0.010 Pleuronectiformes 5* 0 

 Pollachius virens 17* 0 HANGING RATIO 

YEAR Stenotomus chrysops 18* 0 <0.33 59 0 

1999 292 0.028 Centropristis striata 2* 0 0.33 421 0.093 

2000 346 0.092 Cynoscion regalis 5* 0 0.5 2,247 0.093 

2001 123 0 Squalus acanthias 23* 0 >0.5 6* 0 

2002 157 0.081 Rajidae 16 0 

2003 145 0.046 Leucoraja ocellata 91 0.087 TWINE SIZE (mm) 

2004 499 0.058 Morone saxatilis 1* 0 0.28 17 0 

2005 369 0.095 Tautoga onitis 21* 0 0.33 9* 2.474 

2006 450 0.119 Groundfish 15* 0 0.40 1* 0 

2007 450 0.123 Osteichthyes 2* 0 0.45 5* 0 

 0.47 15* 0 

FISH SAMPLING? SURFACE TEMPERATURE (oC) 0.52 43* 0 

yes 1,014 0.050 2-4 8* 0 0.57 173 0.018 

no 1,815 0.118 4-6 477 0.126 0.62 330 0 

 6-8 511 0.090 0.66 154 0.044 

WIND SPEED (kts) 8-10 641 0.087 0.70 149 0 

0-10 1,411 0.104 10-12 524 0.031 0.74 22* 0.106 

10-20 933 0.092 12-14 194 0 0.81 186 0.047 

20-40 174 0 14-16 25* 0 0.9 1,440 0.083 

 1.05 12 0 

STEAM TIME (hrs) BOTTOM TEMPERATURE (oC) unknown 270 0.149 

0-5 1,727 0.032 2-4 170 0.068 

5-10 624 0.200 4-6 547 0.182 MESH SIZE (in) 

10-15 415 0.015 6-8 754 0.102 4-6 53* 0 

15-40 57 0.096 8-10 389 0.035 6-8 551 0 

 10-12 483 0.034 8-10 34 0 

 12-14 20 0 10-12 2,118 0.097 

 12-14 71 0 
49

Table 14 (cont). For the Cape Cod region, observed bycatch rates (Byc Rate) of harbor porpoises 

(Phocoena phocoena) and numbers of observed hauls (Num Obs) for various gear characteristics, 

fishing practices, and environmental factors. The bycatch rate was defined as observed number 

of takes per the observed mtons landed. The overall average bycatch rate was 0.089 harbor 

porpoises per mtons landed. 

Categories of factors with * in the Num Obs column had less than 11 mtons landed (thus given the 

overall bycatch rate for this region, there was a small chance of observing a take). 

High bycatch rates (≥ 0.1 harbor porpoises per mtons landed) are highlighted. 

Data were collected from January – May, 1999 – 2007, and December 1999 – 2006. 

Categories 

Num 

Obs 

Byc 

Rate Categories 

Num 

Obs 

Byc 

Rate Categories 

Num 

Obs 

Byc 

Rate 

LENGTH OF TIE DOWN (ft) NET HEIGHT (ft) USED ANCHORS? 

0-2 254 0.047 0-5 97 0 no 14* 0 

2-4 2,071 0.093 5-10 759 0.068 yes 2,817 0.089 

4-6 129 0.096 10-15 1,353 0.108 

6-10 21* 0 15-25 37* 0 USED ADDED WEIGHTS? 

 no 2,077 0.086 

NUMBER OF ANCHORS NUMBER OF SPACES yes 116 0.300 

1 8* 0 0-5 348 0.108 unknown 637 0.067 

2 2,082 0.083 5-10 657 0.106 

4 30 0 10-15 458 0.075 ANCHOR WEIGHT TYPE 

 15-20 161 0.104 unknown 25* 0 

VESSEL GROSS TONNAGE 20-25 38 0.032 

Danforthtype 507 0.066 

0-20 458 0.082 25-40 23 0.209 Dead Weight 2,298 0.095 

20-40 343 0.157 

40-60 63 0 ANCHOR WEIGHT (lbs) DEPTH OF LEAD LINE (fa) 

60-80 34 0 0-50 1,441 0.087 0-25 985 0.028 

80-140 30 0.428 50-100 870 0.105 25-50 557 0.167 

 100-150 314 0.036 50-75 392 0.073 

AMOUNT OF DISCARDS (lbs) 150-200 147 0.152 75-100 109 0.018 

0-500 884 0.048 200-350 33 0 100-200 83 0 

500-1,000 55 0.082 

1,000-5,000 27 0.054 AMOUNT LANDED (mtons) 

CHLOROPHYLL α

CONCENTRATION (mg/m3

) 

 0-1 2,625 0.106 0 - 1 477 0.094 

SEDIMENT TYPE 1-2 138 0.058 1 - 2 688 0.050 

clay-silt/sand 545 0.089 2-3 27 0.046 2 - 3 328 0.100 

gravel-sand 194 0 3-4 5 0.114 3 - 12 132 0.075 

sand 1,441 0.057 4-7 7 0 

sand-clay/silt 191 0.119 USED PINGERS? 

sand/silt/clay 10* 0.200 yes 1,055 0.053 

 no 1,776 0.098 
50

Table 14 (cont). For the Cape Cod region, observed bycatch rates (Byc Rate) of harbor porpoises 

(Phocoena phocoena) and numbers of observed hauls (Num Obs) for various gear characteristics, 

fishing practices, and environmental factors. The bycatch rate was defined as observed number 

of takes per the observed mtons landed. The overall average bycatch rate was 0.089 harbor 

porpoises per mtons landed. 

Categories of factors with * in the Num Obs column had less than 11 mtons landed (thus given the 

overall bycatch rate for this region, there was a small chance of observing a take). 

High bycatch rates (≥ 0.1 harbor porpoises per mtons landed) are highlighted. 

Data were collected from January – May, 1999 – 2007, and December 1999 – 2006. 

Categories 

Num 

Obs 

Byc 

Rate Categories 

Num 

Obs 

Byc 

Rate Categories 

Num 

Obs 

Byc 

Rate 

WINTER NORTH ATLANTIC 

OSCILLATION INDEX 

NORTH ATLANTIC 

OSCILLATION INDEX LOG10(CHLOROPHYLL α) 

-0.4 - 0 671 0.088 -2.0 - -1.5 19* 0.227 -0.6 - -0.2 171 0.069 

0 - 0.2 110 0.072 -1.5 - -1 431 0.091 -0.2 - 0 306 0.113 

0.2 - 0.4 972 0.073 -1 - -0.5 204 0 0.0 - 0.2 430 0.062 

0.4 - 0.6 248 0.033 -0.5 - 0 518 0.081 0.2 - 0.4 459 0.068 

0.6 - 1.2 380 0.085 0.0 - 0.5 361 0.054 0.4 - 0.6 216 0.056 

 0.5 - 1.0 200 0.022 0.6 - 1.2 43* 0 

WAVE HEIGHT (ft) 1.0 - 1.5 385 0.123 

0-2 1,127 0.120 1.5 - 2.0 263 0 IN A MANAGEMENT AREA? 

 2-4 1,022 0.086 1.5 - 2.0 263 0 yes 1,665 0.066 

4-6 316 0.047 no 1,166 0.102 

6-8 95 0.072 BOTTOM SLOPE (o angle) 

8-10 46 0 0-1 2,263 0.082 BOTTOM DEPTH (fm) 

 1-2 77 0.023 0-50 1,794 0.080 

SOAK DURATION (hrs) 2-4 25 0.049 50-100 544 0.141 

0-100 1,971 0.074 4-8 16* 0 100-150 336 0.044 

100-200 723 0.095 150-200 91 0.016 

200-300 112 0.154 USED TIE DOWNS? 200-350 54 0 

300-500 18* 0.214 no 320 0 

 yes 2,499 0.094 USED SPACES? 

 unknown 12* 0 no 1,121 0.080 

 yes 1,699 0.099 

 unknown 11* 0 
51

Table 15. Models of the bycatch rates of harbor porpoises (Phocoena phocoena) in the Cape Cod 

region. The last column is the difference in the Akaike Information Criterion (AIC) from the row 

above. The larger the difference, the more that factor contributed to explaining the bycatch rate 

patterns. The lower the AIC, the better the model fits.

Model 

number Factors AIC 

Difference 

from 

above 

1 None 631 0 

2 Steam time 579 52 

3 Above + day of the year 543 36 

4 Above + twine size 519 24 

5 Above + temporary home state 500 19 
52

January

February

March

April

May

June

July

August

September

October

November

Decembe

month

0

20406080

100120140160180200220240260280300 1999

20002001200220032004200520062007average

Number of observed hauls

Figure 17. Numbers of observed hauls per month and year in the Cape Cod region. 
53

Figure 18. Locations of observed hauls by month (colored circles) and of observed hauls with harbor porpoise takes (white diamonds) in the Cape Cod region, which includes the Cape Cod South management area (MA) (sfrom January – May in 1999–2007 and December 1999–2006. Depth contours are 50, 100, 200, and 1000 m.
54

Figure 19. Locations of observed hauls by year (colored circles) and of observed hauls with harbor porpoise 

takes (white diamonds) in the Cape Cod region, which includes the Cape Cod South management area (MA) (sh

January – May 1999–2007 and December 1999–2006. Depth contours are 50, 100, 200, and 1000 m.
55

Figure 20. Locations of observed hauls without harbor porpoise (Phocoena phocoena) takes (small black dots) an

takes indentified to year (colored circles) for hauls within the Cape Cod region, which includes the Cape Cod So

(MA) (shaded blue). Data are from January – May 1999–2007 and December 1999–2006. Depth contours are 50, 10
56

Figure 21. Locations of observed hauls without harbor porpoise (Phocoena phocoena) takes (black dashes) an

takes, where the numbers of takes per haul is identified. Size of stack indicates number of takes: dash repre

stack represents three animals per haul. Data are from Cape Cod region, which includes the Cape Cod South m(shaded blue), and are from January – May 1999–2007 and December 1999–2006. Depth contours are 50, 100, 200, 
57

0 2 4 6 8 10 12 14 16 18 20

Steam time (hrs)

-2.0 -1.5 -1.0 -0.5 0.0 0.5

relative bycatch rate

0 30 60 90 120 150 180 210 240 270 

Day of the year

-2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5

relative bycatch rate

0.4 0.6 0.8 1.0

twine size (mm)

-1 0 1 2

relative bycatch rate

0 5 10 15 20 25 30

relative bycatch rate

temporary home state

ME

R

NY

NH-NJ

CT

MA

Figure 22. Results of model describing the bycatch rates of harbor porpoises (Phocoena phocoena) in the Cape 

one plot per factor that was included in the model. Tick marks on the x–axis indicate the values of the observationare jittered (spread out) to help display where there are values that are shared by many observations. The srepresents the overall pattern of these many observations and indicates the best estimate of the bycatch rate at t

variable. The dashed horizontal line indicates the average relative bycatch rate (y = 0), and values along the 

difference relative to this average. Values above this line have higher than average bycatch rates, and those beloaverage bycatch rate.
58

Figure 23. Locations of observed hauls by their fishing vessels’ steam time in hrs from their port (colored sym

hauls with harbor porpoise (Phocoena phocoena) takes (white diamonds) in the Cape Cod region, which include

management area (MA) (shaded blue). Steam times of 4.6–9.4 hrs (green boxes) were identified in the bycatch ratthe highest bycatch rates. Data are from January – May 1999–2007 and December 1999–2006. Depth contours are m.
59

Figure 24. Locations of observed hauls by the vessels’ temporary home state for the trip (colored circles) and o

harbor porpoise (Phocoena phocoena) takes (white diamonds) in the Cape Cod region, which includes management area (MA) (shaded blue). Data are from January – May 1999–2007 and December 1999 – 2006. Depth 

200, and 1000 m.
60

Figure 25. Locations of observed hauls by their fishing vessels’ steam time, in hrs, from their port and temporarcircles) and of observed hauls with harbor porpoise (Phocoena phocoena) takes (white diamonds) in the Caincludes the Cape Cod South management area (MA) (shaded blue). Steam times of 4.6–9.4 hrs (area with hig

divided by the vessels’ temporary home state (defining finer resolution of areas with highest bycatch rates). T

circle had the highest bycatch rate, and the area in the larger black circle had the next highest bycatch rate. DaMay, 1999–2007, and December 1999–2006. Depth contours are 50, 100, 200, and 1000 m.
61

5. GULF OF MAINE REGION 

5.1 Summary 

The Gulf of Maine region (Figure 1) is the northern portion of the Northeast gillnet fishery and 

includes five HPTRP management areas (Northeast, Mid–Coast, Massachusetts Bay, Offshore, 

and Cashes Ledge MAs) and two other relevant areas (Western Gulf of Maine Closure Area 

[WGOM CA] and the Stellwagen Bank Area). Since the implementation of the HPTRP, the 

NEFOP observed 20,758 gillnet hauls in the Gulf of Maine region. In this region, 104 harbor 

porpoises were observed taken, most of which were within the Mid–Coast and Massachusetts 

Bay MAs, and within the nearby areas that were outside the management areas. Highest average 

bycatch rates were in February and November and occurred in 2005. 

Few hauls were observed in the times and areas that were totally closed to gillnets, as defined by 

the HPTRP. Compliance to the required number of pingers dropped substantially in 2003 and 

started increasing again in 2006. 

A statistical model that best predicted the bycatch rates in this region included the following 

factors (in order of importance): area, sea surface temperature, NAO index value, average mesh 

size (in), and total amount of leadline weights (lbs). One way to interpret this model is that the 

factors that provided the most explanation of the bycatch rates patterns were time/area factors 

(area, SST, and NAO), where SST and NAO helped explain the annual and monthly variations. 

Then within these times and areas, the factors that indicated which hauls had the highest bycatch 

were gear characteristics (average mesh size and leadline total weight). 

5.2 Observer Coverage 

In the Gulf of Maine region (Figure 1) from 1 January 1999 – 31 May 2007, there were 20,758 

hauls observed (Table 16), which were from 4,766 trips and 246 unique vessels. This represents 

1,421 – 4,102 observed hauls per year, from 311 – 1,010 trips per year, and from 66 – 146 

vessels per year (Table 16A). The number of hauls observed within each management area 

varied by month (Figure 26). 

Because there was at least one observed take in each month in some part of the Gulf of Maine 

region during at least one year (Table 17), further analyses focused on the Gulf of Maine region 

for all months from 1 January 1999 – 31 May 2007. There were no hauls observed in the 

Northeast MA (Figure 27) at any time of the year after 1 January 1999, so this management area 

will not be discussed further. 

5.3 General Bycatch Patterns 

In the Gulf of Maine region 1 January 1999 – 31 May 2007, most of the harbor porpoise bycatch 

was close to shore within the Mid–coast and Massachusetts Bay MAs and within the nearby 

areas that were outside these two management areas (Figure 27). Hauls with takes were 

observed in the Gulf of Maine region every year, with the most observed takes in 2005 (Table 

16). Takes within a year were usually spread out in more than one area (Figure 28). Hauls with 

takes were observed in the Gulf of Maine region during every month, though not every month in 

each year, where the majority of the takes were in October – December (Table 17). Takes within 

a month were usually spread out in more than one area (Figure 29). Most of the observed hauls 

(93%) that had a harbor porpoise take caught 1 harbor porpoise (89 hauls), 6 hauls caught 2 
62

harbor porpoises (6%) and 1 haul caught 3 harbor porpoises (1%). Hauls that caught multiple 

animals were spread out in several areas (Figure 30). 

Bycatch rates differed by area (Tables 16B–16H). The two areas with the highest bycatch rates 

were the WGOM CA (Table 16F) and the Mid–coast MA (Table 16D). Over all years and 

months, the bycatch rate was 0.056 harbor porpoises per mtons landed from the WGOM CA and 

0.052 harbor porpoises per mtons landed from the Mid–coast MA. The area with the next 

highest bycatch rate was the Stellwagen Bank Area (Table 16G), with a bycatch rate of 0.040 

harbor porpoises per mton landed. The Offshore MA did not have any observed bycatch. 

Harbor porpoise bycatch was observed in each month of the year, where the highest average 

bycatch rates were in February and November (Table 17). On a smaller time/area scale, the 

highest bycatch rates were in the Massachusetts Bay and Mid–coast MAs during March, in the 

WGOM CA and Stellwagen Bank Area during February, and during November and December in 

the Massachusetts Bay and Mid–coast MAs, WGOM CA, and Stellwagen Bank Area (Table 17). 

Bycatch rates (number of observed harbor porpoises per observed mtons landed) of 

categorizations of many factors are listed in Table 18. Some of the values of factors with high 

bycatch rates include: hauls targeting monkfish, the year 2005, water depths of 50–100 fa, 

surface water temperatures of 0–10oC, bottom water temperatures of 2–4oC, long soak durations 

(>96 hrs), long gillnet strings (>5,000 ft), mesh sizes of 8–10 in, twine sizes of 0.70 and 0.74 

mm, large spaces between the panels within a string (>10 ft), gillnet heights of 10–15 ft, leadline 

depths at 30–40 fa (net may not be touching the bottom), 400–800 lbs of leadline weights, 

vessels that were 30–40 gross tons, and times with negative NAO index values. 

5.4 Compliance 

Few hauls were observed in the times and areas that were totally closed to gillnets as required by 

the HPTRP (Table 17). Within the WGOM CA (closed year round since May 1998) there was 

observed fishing during nearly every month, where most observed hauls were close to a border, 

in particular the western border (Figure 27), and harbor porpoise bycatch was observed 

December – March (Table 17). 

Pinger compliance dropped substantially in 2003 in each HPTRP management area and started 

increasing again in 2006 (Figure 31). Compliance in this figure was expressed as observed hauls 

with greater than 90% of the required number of pingers, which reflects the commonly used 10–

net string missing one pinger (which could have fallen off accidently). When expressing 

compliance as 100% of the required number of pingers in the Gulf of Maine region, compliance 

was highest in 1999 (about 75%), dropped to a low in 2003 and 2004 (about 10%), and rose 

again January – May 2007 (about 60%; Figure 32). 

Bycatch rates of strings that had varying levels of compliance were discussed in detail in Palka et 

al. (2008). For example, during 1 January 1999 – 31 May 2007, in the Mid–Coast MA during 

times pingers were required, the harbor porpoise bycatch rate of hauls without any pingers was 

0.017 harbor porpoises/haul. In the same time and area, the bycatch rate of hauls with all of the 

required number of pingers was 0.008 harbor porpoises/haul; that is less than half the rate than 

that of hauls without pingers. The bycatch rates of hauls with 90% or more and 80% or more of 

the required number of pingers were 0.011 and 0.014 harbor porpoises/haul, respectively. The 

same pattern was observed if the bycatch rate was defined as harbor porpoises/mtons landed, 

when looking only at the fall (September – December) or only the winter (January – May) and 

when data from all Gulf of Maine HPTRP management areas were pooled. 
63

5.5 Correlated Factors

The model that best predicted the bycatch rate patterns in the Gulf of Maine region included the 

following factors (in order of importance): area, SST, NAO index value, average mesh size (in), 

and total amount of leadline weights (lbs; Table 19). Figure 33 indicates the values of each 

factor (x–axis) that had higher than average bycatch rates, where y=0 represents an average 

bycatch rate and y-values greater than zero (above the dashed horizontal line) represents higher 

than average bycatch rates. 

One way to interpret this model is that the factors that provide the most explanation of the 

bycatch rates patterns are time/area factors (area, SST, and NAO index value), where SST and 

the NAO index value helped explain variability between the years and between the months. 

Then within these times and areas, the factors that indicated which hauls had the highest bycatch 

were gear characteristics (average mesh size and leadline total weight). A description of each 

factor follows. 

The factor that contributed the most to predicting the bycatch rate patterns within the Gulf of 

Maine region was area. Bycatch rates ranged from no observed bycatch in the Offshore MA to 

rates over 0.05 harbor porpoises per mton landed in the Mid–Coast MA and WGOM CA. 

The factor that contributed the second most was the SST. In general, higher bycatch rates were 

in cooler waters (SST ≤12.5°C [54.5°F]) (Figure 33). The 2–factor model can be interpreted as 

indicating that within each area, bycatch rates were higher when the SST was ≤12.5°C (Table 

20A). 

The next factor, NAO, further refined the bycatch rate patterns. In general, the bycatch rate was 

higher during years when the NAO index value was negative or slightly positive (≤0.15). That 

is, the 3–factor model can be interpreted as indicating that within a particular area and in cooler 

waters (≤12.5°C), the highest bycatch rates were in years when the NAO index value was small, 

≤0.15 (Table 20B). 

The next two factors in the model were gear characteristics. First, average mesh size was 

chosen. In general, bycatch rates were higher for strings using mesh sizes ≥7 in (Figure 33). The 

4–factor model can then be interpreted as indicating that hauls with the highest bycatch rates 

were (within most areas) in waters that were cooler (≤12.5°C), in years with a small NAO index 

value (≤0.15), and strings with large mesh sizes (≥7 in) (Table 20C). 

Lastly, the total pounds of leadline weights were chosen for the model. In general, the more the 

leadline weights, the higher the bycatch rate, except for hauls targeting red hake (Urophycis 

chuss) or white hake (Urophycis tenuis) which use a lot of leadlines weights (≥1,600 lbs) and 

still have no observed harbor porpoise bycatch (Figure 33). Thus, the three groups of leadline 

weights were able to identify the hake hauls which have no observed bycatch and have very 

heavy leadline weights. The 5–factor model can then be interpreted as defining hauls with the 

highest bycatch rates as hauls that (within each area) were in waters that were cooler (≤12.5°C), 

in years with a small NAO index value (≤0.15), used large mesh sizes (≥7 in), and used leadline 

weights of 400–1600 lbs (Table 20D).
64

Table 16. Descriptive statistics of bycatch of harbor porpoises (Phocoena phocoena) in the Gulf of 

Maine region from 1 January 1999 – 31 May 2007, for all areas and each area separately. 

 * Data in the 2007 column are only from 1 January – 31 May, while data from the other years are 

for the full year.

A. All of the Gulf of Maine region

Year 

1999 2000 2001 2002 2003 2004 2005 2006 2007* Total 

Number of observed 

hauls 2453 2742 1967 1642 2094 4102 3711 1421 626 20758

Number of observed 

trips 451 628 417 399 563 1010 865 311 122 4766

Number of observed 

vessels 81 87 66 72 99 146 121 111 55 246

Number of observed 

hauls with one or more 

take 11 9 1 8 9 13 36 8 1 96

Total number of 

observed takes 13 10 2 8 9 14 39 8 1 104

Bycatch rate (observed 

takes/observed number 

of hauls) 0.005 0.004 0.001 0.005 0.004 0.003 0.011 0.006 0.002 0.005

Bycatch rate (observed 

takes/observed mtons 

landed) 0.015 0.018 0.005 0.025 0.022 0.017 0.043 0.023 0.009 0.022

B. Cashes Ledge management area

Year 

1999 2000 2001 2002 2003 2004 2005 2006 2007* Total 

Number of observed hauls 50 0 9 5 4 73 57 8 15 221

Number of observed trips 8 0 2 1 2 8 10 2 2 35

Number of observed vessels 5 0 2 1 1 6 7 2 2 17

Number of observed hauls 

with one or more take 0 0 0 0 2 0 0 0 0 2

Total number of observed 

takes 0 0 0 0 2 0 0 0 0 2

Bycatch rate (observed 

takes/observed number of 

hauls) 0 0 0 0 0.500 0 0 0 0 0.009

Bycatch rate (observed 

takes/observed mtons 

landed) 0 0 0 0 1.159 0 0 0 0 0.023
65

Table 16 (cont). Descriptive statistics of bycatch of harbor porpoises (Phocoena phocoena) in the 

Gulf of Maine region from 1 January 1999 – 31 May 2007, for all areas and each area separately. * 

Data in the 2007 column are only from 1 January – 31 May, while data from the other years are for 

the full year.

C. Massachusetts Bay management area

Year 

1999 2000 2001 2002 2003 2004 2005 2006 2007* Total 

Number of observed 

hauls 331 332 249 304 667 889 536 168 78 3554

Number of observed trips 80 95 60 91 208 282 160 61 34 1071

Number of observed 

vessels 16 19 17 19 36 44 36 29 22 94

Number of observed 

hauls with one or more 

take 0 0 0 2 1 0 5 0 0 8

Total number of observed 

takes 0 0 0 2 1 0 5 0 0 8

Bycatch rate (observed 

takes/observed number of 

hauls) 0 0 0 0.007 0.001 0 0.009 0 0 0.002

Bycatch rate (observed 

takes/observed mtons 

landed) 0 0 0 0.048 0.010 0 0.084 0 0 0.016

D. Mid–coast management area

Year 

1999 2000 2001 2002 2003 2004 2005 2006 2007* Total 

Number of observed 

hauls 476 573 445 502 428 1271 1308 323 19 5345

Number of observed 

trips 133 198 161 169 165 376 350 93 7 1652

Number of observed 

vessels 26 34 24 37 41 76 73 49 7 137

Number of observed 

hauls with one or more 

take 8 6 1 5 4 5 16 3 1 49

Total number of 

observed takes 9 7 2 5 4 6 19 3 1 56

Bycatch rate (observed 

takes/observed number 

of hauls) 0.019 0.012 0.004 0.010 0.009 0.005 0.015 0.009 0.053 0.010

Bycatch rate (observed 

takes/observed mtons 

landed) 0.062 0.075 0.033 0.069 0.045 0.024 0.063 0.043 1.229 0.052
66

Table 16 (cont). Descriptive statistics of bycatch of harbor porpoises (Phocoena phocoena) in the 

Gulf of Maine region from 1 January 1999 – 31 May 2007, for all areas and each area separately. * 

Data in the 2007 column are only from 1 January – 31 May, while data from the other years are for 

the full year.

E. Offshore management area 

Year 

1999 2000 2001 2002 2003 2004 2005 2006 2007* Total

Number of observed hauls 280 162 103 31 59 96 127 142 139 1139

Number of observed trips 24 15 11 7 5 14 19 12 11 118

Number of observed vessels 16 8 7 5 4 11 12 9 8 42

Number of observed hauls 

with one or more take 0 0 0 0 0 0 0 0 0 0

Total number of observed 

takes 0 0 0 0 0 0 0 0 0 0

Bycatch rate (observed 

takes/observed number of 

hauls) 0 0 0 0 0 0 0 0 0 0

Bycatch rate (observed 

takes/observed mtons landed) 0 0 0 0 0 0 0 0 0 0

F. Western Gulf of Maine closed area (from multispecies fishery management plan) 

Year 

1999 2000 2001 2002 2003 2004 2005 2006 2007* Total 

Number of observed 

hauls 62 130 58 53 47 114 154 96 14 728

Number of observed trips 36 55 36 31 19 58 79 39 9 362

Number of observed 

vessels 13 16 14 13 11 24 27 19 7 60

Number of observed 

hauls with one or more 

take 0 2 0 1 0 1 3 3 0 10

Total number of 

observed takes 0 2 0 1 0 1 3 3 0 10

Bycatch rate (observed 

takes/observed number 

of hauls) 0 0.125 0 0.077 0 0.042 0.111 0.158 0 0.014

Bycatch rate (observed 

takes/observed mtons 

landed) 0 0.076 0 0.105 0 0.025 0.073 0.138 0 0.056
67

Table 16 (cont). Descriptive statistics of bycatch of harbor porpoises (Phocoena phocoena) in the 

Gulf of Maine region from 1 January 1999 – 31 May 2007, for all areas and each area separately. * 

Data in the 2007 column are only from 1 January – 31 May, while data from the other years are for 

the full year.

G. Stellwagen Bank area 

Year 

1999 2000 2001 2002 2003 2004 2005 2006 2007* Total 

Number of observed 

hauls 201 265 191 117 193 618 609 285 245 2724

Number of observed 

trips 63 101 61 44 72 197 182 84 66 870

Number of observed 

vessels 19 27 20 14 23 36 32 30 27 83

Number of observed 

hauls with one or more 

take 0 0 0 0 1 6 9 2 0 18

Total number of 

observed takes 0 0 0 0 1 6 9 2 0 18

Bycatch rate (observed 

takes/observed number 

of hauls) 0 0 0 0 0.043 0.167 0.281 0.067 0 0.007

Bycatch rate (observed 

takes/observed mtons 

landed) 0 0 0 0 0.032 0.065 0.104 0.06 0 0.040

H. Outside all the above areas 

Year 

1999 2000 2001 2002 2003 2004 2005 2006 2007* Total 

Number of observed 

hauls 1053 1280 912 630 696 1041 920 399 116 7047

Number of observed 

trips 178 237 169 127 136 190 193 77 17 1324

Number of observed 

vessels 36 42 37 36 39 46 37 37 12 120

Number of observed 

hauls with one or more 

take 3 1 0 0 1 1 3 0 0 9

Total number of 

observed takes 4 1 0 0 1 1 3 0 0 10

Bycatch rate (observed 

takes/observed number 

of hauls) 0.111 0.024 0 0 0.026 0.022 0.081 0 0 0.001

Bycatch rate (observed 

takes/observed mtons 

landed) 0.011 0.004 0 0 0.007 0.003 0.009 0 0 0.005
68

Table 17. Within the Gulf of Maine (GOM) region, by month and area: (A) number of observed 

harbor porpoise (Phocoena phocoena) takes and observed hauls (in parentheses) and (B) 

resulting bycatch rates (harbor porpoises per mtons landed). Data from 1 January 1999 – 31 May 

2007. Dark shaded cells indicate the times and areas when pingers are required. Light shaded 

cells with bold numbers indicate the times and areas that are closed to all gillnets under the 

harbor porpoise take reduction plan.

A. Number of observed harbor porpoise takes (Number of observed hauls) 

Month 

Cashes 

Ledge 

Massachusetts 

Bay Mid-coast Offshore 

Western 

GOM 

Stellwagen 

Bank 

Outside these 

areas All areas 

1999 – 2007 

Jan 0 (0) 0 (273) 1 (139) 0 (55) 1 (67) 3 (377) 0 (433) 5 (1,344) 

Feb 0 (21) 0 (193) 0 (177) 0 (79) 2 (98) 7 (396) 0 (281) 9 (1,245) 

Mar 0 (13) 1 (61) 3 (199) 0 (95) 1 (153) 2 (499) 1 (370) 8 (1,390) 

Apr 0 (13) 0 (0) 0 (30) 0 (145) 0 (0) 0 (0) 5 (649) 5 (837) 

May 0 (0) 0 (326) 0 (5) 0 (77) 0 (22) 0 (200) 1 (614) 1 (1,244) 

1999 – 2006 

Jun 2 (24) 0 (721) 1 (195) 0 (124) 0 (29) 0 (286) 0 (639) 3 (2,018) 

Jul 0 (0) 0 (397) 2 (944) 0 (127) 0 (60) 0 (210) 0 (630) 2 (2,368) 

Aug 0 (30) 0 (488) 1 (888) 0 (82) 0 (67) 0 (214) 0 (746) 1 (2,515) 

Sep 0 (36) 2 (496) 4 (728) 0 (46) 0 (67) 0 (252) 0 (806) 6 (2,431) 

Oct 0 (53) 0 (38) 11 (790) 0 (150) 0 (60) 0 (5) 0 (722) 11 (1,818) 

Nov 0 (18) 2 (95) 26 (925) 0 (83) 5 (74) 0 (5) 1 (681) 34 (1,881) 

Dec 0 (13) 3 (466) 7 (325) 0 (76) 1 (31) 6 (280) 2 (476) 19 (1,667) 

Total 2 (221) 8 (3,554) 56 (5,345) 0 (1,139) 10 (728) 18 (2,724) 10 (7,047) 104 (20,758) 
69

B. Bycatch rate (harbor porpoises per mtons landed) 

Month 

Cashes 

Ledge 

Massachusetts 

Bay Mid-coast Offshore 

Western 

GOM 

Stellwagen 

Bank 

Outside these 

areas All areas 

1999 – 2007 

Jan 0 0 0.045 0 0.082 0.047 0 0.022 

Feb 0 0 0 0 0.192 0.192 0 0.056 

Mar 0 0.267 0.156 0 0.047 0.037 0.017 0.038 

Apr 0 0 0 0 0 0 0.069 0.040 

May 0 0 0 0 0 0 0.010 0.005 

1999 – 2006 

Jun 0.332 0 0.032 0 0 0 0 0.007 

Jul 0 0 0.010 0 0 0 0 0.003 

Aug 0 0 0.006 0 0 0 0 0.002 

Sep 0 0.023 0.028 0 0 0 0 0.010 

Oct 0 0 0.066 0 0 0 0 0.023 

Nov 0 0.052 0.121 0 0.145 0 0.005 0.066 

Dec 0 0.043 0.071 0 0.095 0.079 0.018 0.044 

Total 0.023 0.016 0.052 0 0.056 0.040 0.005 0.022 
70

Table 18. For the Gulf of Maine region, observed bycatch rates (Byc Rate) of harbor porpoises 

(Phocoena phocoena) and numbers of observed hauls (Num Obs) for various gear characteristics, 

fishing practices, and environmental factors. The bycatch rate was defined as observed number 

of takes per observed mtons landed. The overall average bycatch rate was 0.022 harbor 

porpoises per mtons landed. 

Categories of factors with * in the Num Obs column had less than 200 observed hauls (thus given 

the overall bycatch rate for this region, there was a small chance of observing a take). 

High bycatch rates (≥ 0.04 harbor porpoises per mtons landed) are highlighted. 

Data were collected from 1 January 1999 – 31 May 2007. 

Categories 

Num 

Obs 

Byc 

Rate Categories 

Num 

Obs

Byc 

Rate Categories 

Num 

Obs Byc Rate

MONTH TARGET SPECIES LENGTH OF STRING (ft) 

Jan 1,344 0.022 Gadus morhua 8,957 0.029 0-1,000 263 0

Feb 1,245 0.056 Pleuronectiformes 1,159 0.027 1,001-2,000 2,186 0.019

Mar 1,390 0.038 Homarus americanus 54* 0 2,001-3,000 5,538 0.026

Apr 837 0.040 haddock 215 0 3,001-4,000 7,978 0.018

May 1,244 0.005 Leptoscopus americanus 3,489 0.042 4,001-5,000 2,451 0.020

Jun 2,018 0.007 Pollachius virens 1,470 0.019 5,001-6,000 671 0.082

Jul 2,368 0.003 Squalus acanthias 681 0.002 6,001-30,000 1,659 0.010

Aug 2,515 0.002 groundfish 1,965 0.016 

Sep 2,431 0.010 Urophycis tenuis 158* 0 TWINE SIZE (mm) 

Oct 1,818 0.023 Pleuronectes americanus 1,231 0 0.28 1* 0

Nov 1,881 0.066 Rajidae 348 0 0.33 16* 0

Dec 1,667 0.044 Pleuronectes ferrugineus 1,016 0.015 0.40 42* 0

 0.45 95* 0.034

YEAR SURFACE TEMPERATURE (oC) 0.47 1,629 0.010

1999 2,453 0.015 0-5 2,927 0.046 0.52 1,635 0.014

2000 2,742 0.018 5-10 4,848 0.048 0.57 4,300 0.017

2001 1,967 0.005 10-15 4,265 0.024 0.62 8,239 0.022

2002 1,642 0.025 15-20 7,551 0.004 0.66 1,539 0.024

2003 2,094 0.022 20-25 519 0 0.70 316 0.088

2004 4,102 0.017 0.74 124* 0.041

2005 3,711 0.043 SPACE WIDTH BETWEEN NETS (ft) 0.81 368 0.011

2006 1,421 0.023 3 12,771 0.015 0.9 1,711 0.025

2007 626 0.009 4 433 0.057 1.05 15* 0

 5+ 809 0.005 unknown 721 0.036
71

Table 18 (cont). For the Gulf of Maine region, observed bycatch rates (Byc Rate) of harbor 

porpoises (Phocoena phocoena) and numbers of observed hauls (Num Obs) for various gear 

characteristics, fishing practices, and environmental factors. The bycatch rate was defined as 

observed number of takes per observed mtons landed. The overall average bycatch rate was 

0.022 harbor porpoises per mtons landed. 

Categories of factors with * in the Num Obs column had less than 200 observed hauls (thus given 

the overall bycatch rate for this region, there was a small chance of observing a take). 

High bycatch rates (≥ 0.04 harbor porpoises per mtons landed) are highlighted. 

Data were collected from 1 January 1999 – 31 May 2007. 

Categories 

Num 

Obs 

Byc 

Rate Categories 

Num 

Obs 

Byc 

Rate Categories 

Num 

Obs 

Byc 

Rate 

WIND SPEED (kts) MESH SIZE (in) 

0-10 10,537 0.026 BOTTOM TEMPERATURE (oC) 2-4 9* 0 

10-20 6,796 0.025 0-2 270 0 4-6 1,493 0.011 

20-30 1,580 0.008 2-4 2,949 0.049 6-8 14,613 0.020 

30-40 119* 0.031 4-6 7,037 0.005 8-10 1,455 0.044 

 6-8 6,613 0.029 10-18 3,153 0.028 

STEAM TIME (hrs) 8-10 3,030 0.033 

0-5 18,186 0.025 10-14 29* 0 USED TIE DOWNS? 

5-10 1,197 0.013 no 15,151 0.019 

10-15 790 0.016 BOTTOM SLOPE (o angle) yes 5,373 0.031 

15-100 549 0 0-0.2 9,866 0.015 unknown 234 0 

 0.2-0.4 9,606 0.033 

BOTTOM DEPTH (fm) 0.4-0.6 609 0.017 USED SPACES? 

0-50 8,831 0.009 0.6-1.2 51* 0.077 no 6,583 0.031 

50-100 7,964 0.048 yes 14,148 0.017 

100-150 1,727 0.007 SOAK DURATION (hrs) unknown 27* 0 

150-200 1,160 0.016 0-12 1,097 0.006 

200-300 398 0 13-24 9,732 0.016 USED DROP LINES? 

 24-36 347 0.008 no 15,549 0.024 

TIE DOWN LENGTH (ft) 36-48 3,483 0.027 yes 6* 0 

0-1 35* 0 48-96 3,837 0.028 unknown 5,196 0.016 

1-2 390 0.054 96-800 2,247 0.045 

2-3 3,258 0.016 USED ANCHORS? 

3-4 1,515 0.038 NET HEIGHT (ft) no 2,104 0.026 

4-5 112* 0 0-5 335 0 yes 18,645 0.021 

>5 135* 0.184 5-10 6,858 0.029 

 10-15 8,090 0.200 USED ADDED WEIGHTS? 

FISH SAMPLING? 15-25 239 0.010 no 15,480 0.025 

yes 11,618 0.019 yes 70* 0 

no 9,134 0.026 Unknown 5,192 0.016 

unknown 6* 0.000 

 
72

Table 18 (cont). For the Gulf of Maine region, observed bycatch rates (Byc Rate) of harbor 

porpoises (Phocoena phocoena) and numbers of observed hauls (Num Obs) for various gear 

characteristics, fishing practices, and environmental factors. The bycatch rate was defined as 

observed number of takes per observed mtons landed. The overall average bycatch rate was 

0.022 harbor porpoises per mtons landed. 

Categories of factors with * in the Num Obs column had less than 200 observed hauls (thus given 

the overall bycatch rate for this region, there was a small chance of observing a take). 

High bycatch rates (≥ 0.04 harbor porpoises per mtons landed) are highlighted. 

Data were collected from 1 January 1999 – 31 May 2007. 

Categories 

Num 

Obs 

Byc 

Rate Categories 

Num 

Obs Byc Rate Categories 

Num 

Obs 

Byc 

Rate 

 

WINTER NORTH ATLANTIC 

OSCILLATION INDEX ANCHOR WEIGHT TYPE

VESSEL GROSS TONNAGE -0.4 - 0 3,741 0.028 unknown 2,215 0.026 

0-10 643 0.029 0 - 0.2 1,965 0.028 

Danforthstyle 3,572 0.013 

10-20 1,356 0.021 0.2 - 0.4 9,317 0.023 Dead Weight 14971 0.023 

20-30 838 0.009 0.4 - 0.6 2,273 0.014 

30-40 388 0.048 0.6 - 1.2 2,836 0.020 LEAD LINE DEPTH (ft)

40-50 151* 0.022 0-20 2,180 0.003 

50-70 123* 0.000 VESSEL LENGTH (ft) 20-30 5,033 0.025 

>70 213 0.041 20-30 37* 0 30-40 3,795 0.049 

 30-40 1,202 0.031 40-50 2,120 0.031 

AMOUNT OF DISCARDS (lbs) 40-45 1,986 0.033 >50 2,300 0.019 

0-250 8,586 0.017 45-50 446 0.017 

250-500 1,308 0.024 50-60 319 0.012 

CHLOROPHYLL α

CONCENTRATION (mg/m3

)

500-1,000 730 0.008 60-80 289 0.028 0-1 3,831 0.019 

1,000-1,500 218 0.073 1-1.5 4,732 0.013 

>1,500 374 0.019 

NORTH ATLANTIC OSCILLATION 

INDEX 1.5-2 2,699 0.021 

 -3 - -2 330 0.050 2-4 3,232 0.022 

SEDIMENT TYPE -2 - -1 1,690 0.028 >4 1,139 0.013 

unknown 486 0.000 -1 - 0 7,740 0.038 

clay 14* 0.000 0-1 7,478 0.011 LOG10(CHLOROPHYLL)

claysilt/sand 1,555 0.021 1-2 2,894 0.007 <0 3,831 0.019 

gravel 985 0.006 0-0.1 2,571 0.011 

gravel-sand 3,506 0.032 NUMBER OF ANCHORS 0.1-0.2 2,658 0.017 

sand 7,518 0.014 1 129* 0.106 0.2-0.4 3,678 0.023 

sandclay/silt 1,049 0.040 2 13,753 0.024 0.4-0.6 1,753 0.020 

sandsilt/clay 1,940 0.039 3 51* 0 >0.6 1,142 0.013 

sand/silt/ 

clay 3,063 0.017 4 81* 0.064 
73

Table 18 (cont). For the Gulf of Maine region, observed bycatch rates (Byc Rate) of harbor 

porpoises (Phocoena phocoena) and numbers of observed hauls (Num Obs) for various gear 

characteristics, fishing practices, and environmental factors. The bycatch rate was defined as 

observed number of takes per observed mtons landed. The overall average bycatch rate was 

0.022 harbor porpoises per mtons landed. 

Categories of factors with * in the Num Obs column had less than 200 observed hauls (thus given 

the overall bycatch rate for this region, there was a small chance of observing a take). 

High bycatch rates (≥ 0.04 harbor porpoises per mtons landed) are highlighted. 

Data were collected from 1 January 1999 – 31 May 2007. 

Categories 

Num 

Obs 

Byc 

Rate Categories 

Num 

Obs 

Byc 

Rate Categories 

Num 

Obs Byc Rate 

 LEAD LINE WEIGHT (lbs) AREAS 

WAVE HEIGHT (ft) 0-200 2,502 0.015 Cashes Ledge 221 0.023 

0-2 8,763 0.027 200-300 3,789 0.008 Mass Bay 3,554 0.016 

2-4 7,011 0.022 300-400 6,793 0.014 Mid-Coast 5,345 0.052 

4-6 2,457 0.019 400-500 2,293 0.033 Offshore 1,139 0 

6-8 643 0.020 500-600 861 0.046 

Western Gulf 

of Maine 728 0.056 

8-10 219 0.014 600-800 1,779 0.046 

Stellwagen 

Banks 2,724 0.040 

 800-1000 947 0.015 other 7,047 0.005 

ANCHOR WEIGHT (lbs) 1000-7000 1,421 0.019 

0-40 1,491 0.067 NUMBER OF SPACES

40-60 7,703 0.016 HANGING RATIO 0-2 242 0.055 

60-80 2,438 0.033 <0.5 2,180 0.024 2-4 1,464 0.022 

80-100 2,616 0.013 0.5 18,491 0.022 4-6 662 0 

100-150 2,482 0.026 >0.5 38* 0 6-8 1,854 0.003 

>150 1,854 0 8-10 6,717 0.018 

 10-15 1,948 0.015 

 15-20 741 0.031 

 20-50 445 0.015 
74

Table 19. Models of the bycatch rates of harbor porpoises (Phocoena phocoena) in the Gulf of 

Maine region. The last column is the difference in the Akaike Information Criterion (AIC) from the 

row above. The larger the difference, the more that factor contributed to explaining the bycatch 

rate patterns. The lower the AIC, the better the model fits. 

Model 

number Factors AIC 

Difference 

from 

above 

1 None 1233 0 

2 Area 1144 89 

3 Above + Sea surface temperature 1066 78 

4 Above + North Atlantic oscillation index 1016 50 

5 Above + Average mesh size 982 34 

6 Above + Leadline weight 963 19 
75

Table 20. Bycatch rates of harbor porpoises (Phocoena phocoena) in the Gulf of Maine region by 

the factors in the bycatch rate model. 

A. Harbor porpoise bycatch rates by area (HPTRP management areas [MA] or fishery 

management plan closed areas [CA]) and sea surface temperature (SST) categories. 12.5°C = 

54.5°F 

SST 

Area 2°–12.5°C >12.5°C

Cashes Ledge MA 0.058 0

Massachusetts Bay MA 0.020 0.006

Mid–coast MA 0.096 0.019

Offshore MA 0 0

WGOM CA 0.096 0

Stellwagen Bank Area 0.067 0

Other areas 0.014 0

B. Harbor porpoise bycatch rates by area (HPTRP management areas [MA] or fishery 

management plan closed areas [CA]), sea surface temperature (SST), and North Atlantic 

oscillation index (NAO) categories. 

SST: 2° – 12.5°C SST: > 12.5°C 

NAO NAO 

Area ≤0.15 >0.15 ≤0.15 >0.15

Cashes Ledge MA 0.104 0 0 0

Massachusetts Bay MA 0.052 0.007 0.012 0

Mid–coast MA 0.153 0.052 0.021 0.016

Offshore MA 0 0 0 0

WGOM CA 0.163 0.049 0 0

Stellwagen Bank Area 0.149 0.006 0 0

Other areas 0.030 0.002 0 0

C. Harbor porpoise bycatch rates by area (HPTRP management areas [MA] or fishery 

management plan closed areas [CA]) and mesh size for hauls that were in 2°–12.5°C waters, and 

years where the North Atlantic oscillation index (NAO) was ≤0.15. 

mesh size (in)

Area <7 ≥7

Cashes Ledge MA 0 0.255

Massachusetts Bay MA 0 0.116

Mid–coast MA 0.071 0.215

Offshore MA 0 0

WGOM CA 0.177 0.147

Stellwagen Bank Area 0 0.183

Other areas 0.033 0.027
76

D. Harbor porpoise bycatch rates by area (HPTRP management areas [MA] or fishery 

management plan closed areas [CA]) and leadline total weight for hauls that were in 2°–12.5°C 

waters, years when the North Atlantic oscillation index (NAO) was ≤0.15 and mesh sizes were 

≥7 in. 

Leadline total weight (lbs)

Area <400 400–1600 >1600

Cashes Ledge MA 0 0.409 0

Massachusetts Bay MA 0.158 0 0

Mid–coast MA 0.047 0.361 0

Offshore MA 0 0 0

WGOM CA 0 0.249 0

Stellwagen Bank Area 0.147 0.203 0

Other Areas 0.013 0.042 0
77

January

February

March

April

May

June

July

August

September

October

November

Decem

Month

0

100200300400500600700800900

100011001200 Cashes Ledge MA

Massachusetts BayMAMid-Coast MAOffshore MAWestern Gulf of Maine CAOutside all areasStellwagen Bank Area

Number of Hauls

Figure 26. Within the Gulf of Maine region by month, numbers of observed hauls within each area (HPTRP mafishery management plan closed areas [CA] and outside these areas). Data are from 1 January 1999 – 31 May 2007
78

Figure 27. Locations of observed hauls without takes of harbor porpoises (Phocoena phocoena) (small dots) antakes (red circles). Data from 1 January 1999 – 31 May 2007 within the Gulf of Maine (GOM) region, which includetake reduction management areas (MA), the Western Gulf of Maine closed area (CA), and the Stellwagen Bank Are50, 100, and 200 m.
79

Figure 28. Locations of observed hauls without takes of harbor porpoises (Phocoena phocoena) (small dots) antakes identified by year (colored circles). Data are from 1 January 1999 – 31 May 2007 within the Gulf of Maine 

includes five harbor porpoise take reduction management areas (MA), the Western Gulf of Maine closed area (CABank Area. Depth contours are 50, 100, and 200 m.
80

Figure 29. Locations of observed hauls without takes of harbor porpoises (Phocoena phocoena) (small dots) antakes identified by month (colored circles). Data are from 1 January 1999 – 31 May 2007 within the Gulf of Maine 

includes five harbor porpoise take reduction management areas (MA), the Western Gulf of Maine closed area (CABank Area. Depth contours are 50, 100, and 200 m.
81

Figure 30. Locations of observed hauls without harbor porpoise (Phocoena phocoena) takes (black dots), and takes, where the numbers of takes per haul are identified. Size of stack indicates number of takes: dot represents 

represents three animals per haul. Data are from 1 January 1999 – 31 May 2007 within the Gulf of Maine (GOM) rfive harbor porpoise take reduction management areas (MA), the Western Gulf of Maine closed area (CA), and the 

Depth contours are 50, 100, and 200 m.
82

1999 2000 2001 2002 2003 2004 2005 2006 

year

0.00.10.20.30.40.50.60.70.80.91.0 Cape Cod South MA

Massachusetts Bay MMid-Coast MAOffshore MA

Proportion of observed hauls that used more than 90%

 of the required number of pingers

Figure 31. In the Gulf of Maine region, by harbor porpoise take reduction management areas (MA), the proportion used greater than 90% of the required number of pingers during times when pingers were required. Data are fro

May 2007.
83

0 20 40 60 80 100 0 20 40 60 80 

0 20 40 60 80 100

Percentage of the required number of pingers per string

0

20406080

0

20406080

1999 2000 20012002 2003 20042005 2006 Jan-May 2007

Percentage of observed hauls within a year

Figure 32. By year, within the Gulf of Maine region, the percentage of the required number of pingers used on gilln
84

-10 -5 0

relative bycatch rate

5 10 15 

Sea surface temperature (

-4 -2 0 2

relative bycatch rate

-2 -1 0 

North Atlantic oscillation ind

-1.5 -0.5 0.5

relative bycatch rate

5 10 1

5

Mesh size (in)

-4 -2 0

relative bycatch rate7.0

12.5

0 1000 2000 3000 4000 50

Lead line total weight (lbs

-15 -10 -5 0

relative bycatch rate1600

0.15

Cashes Ledge MA

Massachusetts Bay MA

Mid-Coast MA

Offshore MA

Western Gulf of Maine CA

Stellwagen Bank Area

outside other areas

Area

Figure 33. Results of model describing the bycatch rates of harbor porpoises (Phocoena phocoena) in the Gulf ois one plot per factor that was included in the model. Tick marks on the x–axis indicate the values of the obsemarks are jittered (spread out) to help display where there are values that are shared by many observationsrepresents the overall pattern of these many observations and indicates the best estimate of the bycatch rate at x-axis variable. The dashed horizontal line indicates the average relative bycatch rate (y = 0), and values along difference relative to this average. Values above this line have higher than average bycatch rates, and those beaverage bycatch rate.
85

REFERENCES 

[NEFSC] Northeast Fisheries Science Center. 2008. Northeast fisheries observer program: 

Fisheries observer program manual. Available from NEFSC, 166 Water St., Woods 

Hole, MA 02543. http://www.nefsc.noaa.gov/femad/fishsamp/fsb/ 

Palka DL, Rossman MC, VanAtten AS, Orphanides CD. 2008. Effect of pingers on harbor 

porpoise and seal bycatch in the US Northeast gillnet fishery. J. Cetacean Res. Manage. 

10(3): 217–226. 

Stenseth NC, Mysterud A, Ottersen G, Hurrell JW, Chan K-S, Lima M. 2002. Ecological effects 

of climate fluctuations. Science 297:1292–1296. 

[USGS] United States Geological Survey. 2000. USGS east-coast sediment analysis and 

georeferenced displays. Available from USGS Woods Hole Field Center, Woods Hole, 

MA 02543. http://pubs.usgs.gov/of/2000/of00-358/ 

Warden ML, Orphanides CD. 2008. Preparation of the Northeast Fisheries Observer Program 

gillnet data for use in bycatch analyses of protected species. US Dept of Commerce, 

Northeast Fisheries Science Center Reference Doc. 08–17; 44 pp. 

http://www.nefsc.noaa.gov/nefsc/publications/crd/crd0817/. 
86

APPENDIX 

Factors used to develop bycatch rate models. For more information on fishing gear related 

characteristics see NEFSC (2008). * Factors with missing values filled in using process described 

in Warden and Orphanides (2008). 

Factor Name Description 

LOCATION AND TIMING 

Day of year Day of year: 1 = January 1st for each year 

Year Year beginning of haul occurred (1999 – 2007) 

Month Month beginning of haul occurred (January – December) 

Longitude* Longitude location of beginning of haul 

Latitude* Latitude location of beginning of haul 

Bottom depth* 

Bottom depth of location of beginning of haul (fa); see Warden and 

Orphanides (2008) for more description of this variable 

Distance to 50 m* 

Distance between location of beginning of haul and the 50 m depth 

contour, resolution 100 m (m) see Warden and Orphanides (2008) 

for more description of this variable 

Distance to 100 m* 

Distance between location of beginning of haul and the 100 m 

depth contour, resolution 100 m (m); see Warden and Orphanides 

(2008) for more description of this variable 

Distance to 200 m* 

Distance between location of beginning of haul and the 200 m 

depth contour, resolution 100 m (m); see Warden and Orphanides 

(2008) for more description of this variable 

Distance to 500 m* 

Distance between location of beginning of haul and the 500 m 

depth contour, resolution 100 m (m); see Warden and Orphanides 

(2008) for more description of this variable 

Distance to the coast* 

Distance from beginning of haul to the nearest coastline, resolution 

1000 m (m) ); see Warden and Orphanides (2008) for more 

description of this variable 

North Atlantic Oscillation7

North Atlantic Oscillation (NAO) monthly mean index for the 

month and year that the beginning of haul occurred; calculated by 

the Climate Prediction Center8

 

7

 The North Atlantic oscillation (NAO) is a climatic phenomenon in the North Atlantic Ocean. It is the difference in 

the atmospheric pressure at sea level between the Icelandic low and Azores high pressure centers. This difference 

controls the strength and direction of westerly winds and storm tracks across the North Atlantic. Especially during 

the months of November – April, the NAO is responsible for much of the variability of weather in the North Atlantic 

region. It affects wind speed and wind direction changes, changes in temperature and moisture distribution and the 

intensity, number, and tracks of storms. A positive NAO index value indicates there is a stronger than usual 

subtropical high pressure center, thus, resulting in more and stronger winter storms that cross the Atlantic on a more 

northerly track. Consequently, the eastern US experiences mild and wet winter conditions, and thus warmer, less 

saline surface waters. This can prevent nutrient-rich upwelling which can reduce productivity and has been shown to 

have effects on terrestrial and marine life (Stenseth et al. 2002). 

8

 Data retrieved from the Climate Prediction Center (http://www.cpc.ncep.noaa.gov/data/teledoc/nao.shtml), 

accessed 21 March 2007. For a description of the methods used to calculate the North Atlantic oscillation (NAO) 

see http://www.cpc.ncep.noaa.gov/data/teledoc/teleindcalc.shtml). 
87

Factor Name Description 

NAO – 17 NAO index from 1 year before the time of the beginning of haul 

NAO – 27 NAO index from 2 years before the time of the beginning of haul 

Winter NAO7

Average of the NAO monthly index means from December – 

March of the year the beginning of the haul occurred in 

Winter NAO – 17

Winter NAO monthly index from 1 year before the time of the 

beginning of haul 

Winter NAO – 27

Winter NAO monthly index from 2 years before the time of the 

beginning of haul 

Sea surface temperature* 

Sea surface temperature (SST) at location and time of beginning of 

haul (°C); see Warden and Orphanides (2008) for more description 

of this variable 

Bottom water temperature* 

Climatological bottom water temperature at location and time of 

beginning of haul (°C); see Warden and Orphanides (2008) for 

more description of this variable 

Bottom slope* 

Bottom slope (° angle) of location of beginning of haul; see 

Warden and Orphanides (2008) for more description of this 

variable 

Chlorophyll α concentration 

Chlorophyll α concentration as derived from satellite data (mg/m3) 

at location and time of beginning of haul; see Warden and 

Orphanides (2008) for more description of this variable 

log10(Chlorophyll α

concentration ) 

log10(chlorophyll α concentration as derived from satellite data) 

[log10 (mg/m3)] ; see Warden and Orphanides (2008) for more 

description of this variable 

Sediment 

Type of bottom sediment at location of beginning of haul as 

derived from CONMAP sediment maps (USGS 2000) 

FISHING PRACTICES 

Soak duration* 

Amount of time gillnet string for this haul is in the water fishing 

(hrs) 

Target species 

Principal species, or species group, sought after in this haul; often 

obtained from captain 

Temporary home port 

Name of the port, including the state, where the vessel left to begin 

the trip 

Vessel gross tonnage 

Total gross registered tonnage of the vessel (ton); often obtained 

from captain 

Vessel length Total length of fishing vessel (ft); often obtained from captain 

Haul duration* Length of time needed to retrieve the string from the ocean (hrs) 

Days absent Number of days absent from a port for the present trip 

State landed State that catch from this trip was landed in 

Weather 

Weather conditions at the beginning of the haul (unknown; clear; 

partly cloudy; continuous layers of clouds; drizzle; rain; showers; 

thunderstorms; rain and fog; fog or thick haze; snow or rain and 

snow mixed; blowing snow; other) 

Wave height Wave height at the beginning of the haul (ft) 
88

Factor Name Description 

Steam time 

Time elapsed between when vessel leaves the dock to go fishing, 

and arrives at the location where the gillnet string is first deployed 

or hauled back (hr) 

GEAR CHARACTERISTICS (Figure A.1)

Twine size Thickness of the twine in the net’s webbing (mm) 

Mesh count* Average number of meshes in the vertical direction of the net 

Gear length* Total length of gillnet string and spaces between nets (ft) 

Net height Average height of a net in the string (ft) 

Average mesh size* 

Average mesh size calculated using the number of nets and their 

corresponding mesh sizes (in) 

Hang ratio* 

Average fractional ratio of the length of the floatline for one net to 

the length that the net would be if it was taken off the floatline and 

stretched out 

Number of nets set Total number of nets that were used for this set 

Number of nets hauled Total number of nets in this set that were hauled back 

Used tie downs?* 

Whether tie downs (line used between the floatline and the leadline 

as a way to create a pocket or bag of netting) were used (yes all 

nets; yes not all nets; no; unknown) 

Length tie downs Average length of tie downs used in string (ft) 

Used anchors?* Whether any anchors were used (yes; no; unknown) 

Number of anchors Number of anchors used on the string 

Type of anchor 

Type of anchor used (Danforth-style; dead weight [i.e., railroad 

tracks, mushroom weights, etc.]; combination; other; unknown) 

Anchor weight Total weight of anchors used to hold string in place (lbs) 

Used additional weights? 

Whether any additional weights were used on the leadline of the 

string (yes; no; unknown) 

Additional weights 

Total amount of the additional weights used on the leadline of the 

string (lbs) 

Used droplines? 

Whether droplines (line connecting the floats on the water’s surface 

to the floatline to suspend the string in the water column) were used

(yes; no; unknown) 

Leadline depth Depth from the surface at which the leadline fishes for this haul (fa)

Weight of leadline Weight of the leadline used in an average net of the string (lbs) 

Used spaces?* 

Whether there were any continuous spaces greater than or equal to 

2.5 feet between the nets in the string (yes; no; unknown) 

Space width Average width of spaces used between the nets in the string (ft) 

Number of spaces Total number of spaces used between the nets in the string 

Color of gillnet 

Color of net webbing used in the string (clear; white; pink; black; 

green; blue; multicolor; red, orange; purple; combination; other; 

unknown) 

Float distance Average distance along the floatline between floats (ft) 

Total number of floats Total number of floats attached to the floatline 
89

Factor Name Description 

OBSERVER PRACTICE 

Biological fish sampling? 

Type of observer protocol 

(Yes means there is complete fish sampling which is where the 

observer records biological data on both the kept and discarded 

catch and if an incidental take is brought on board then the take is 

worked up using the protected species take protocols; 

No means there is limited fish sampling which is where the 

observer records only the amount of kept catch and observer 

conducts protected species haul watch, which means the observer 

watches the net as it is being hauled from the water to document 

any incidental takes that fall out of the net before the take is 

brought on board) 
90

Figure A.1. Configuration of typical gillnet string (gear). Taken from NEFSC (2008).