# Presentation: 409737

## Western Atlantic Pelagic Longline Sea Turtle Mitigation Research2001 - 2003John Watson, Dan Foster, Sheryan Epperly, Arvind Shah

**Notes:**
NOAA Fisheries in cooperation with the Blue Water Fishermen’s Association  conducted research in the Western Atlantic Ocean to develop and evaluate fishing gear modifications and tactics to reduce the incidental capture of endangered and threatened sea turtle species by pelagic longline fishing gears. A three year project was initiated in 2001 and was completed in 2003. The following presentation is a summary of the results of this research. 

## Geographical distribution of the US Atlantic Pelagic Longline fishery

- Courtesy of Mauricio Ortiz

**Notes:**
The area of operation was the Northeast Distant Waters (NED) statistical reporting zone in the Western Atlantic Ocean. The NED area is closed to pelagic longline fishing by U.S. flag vessels by regulation with the exception of the experimental fishery. 

## 2001 Experiments

- Controls were natural squid on 8/0, 9/0, or 10/0 J-hooks (25°-30° offset) and a branch line directly under every float.
- Treatments
- Blue-dyed Squid bait
- Move branch line 20 fathoms away from every float
- Investigate variables which may affect turtle interactions

**Notes:**
In 2001 the research experimental design was to test the effect of moving hooks that are normally deployed very near floats to 20 fathoms away from floats as historical data indicates a higher turtle take proportion on the hooks nearest floats. The design also tested the effect of using blue dyed squid rather than the standard squid as bait. Data on eighteen other variables were also collected to determine their effect on turtle capture rates. 

## 2002 Experiments

- Controls were natural squid on 9/0 J-hooks (25°-30° offset).
- Treatments
- Reduce daylight hook soak time
- 18/0 circle hooks (non offset)
- 18/0 circle hooks (10°  offset)
- Mackerel bait

**Notes:**
In 2002 the experimental design evaluated the effect of reducing daylight hook soak time, the use of 18/0 circle hooks both offset and non offset with squid bait, and the use of mackerel bait on both J hooks (control) and 18/0 circle hooks in reducing sea turtle interactions with pelagic longline gear.   

## 2003 ExperimentsSwordfish Sets

- Controls were natural squid on 25°-30° offset 9/0 J-hooks.
- Treatments
- Non offset 18/0 circle hooks with squid
- 10°  offset 18/0 circle hooks with mackerel
- 10° offset 20/0 circle hooks with mackerel
- 10/0 non offset tuna hook with mackerel bait.
- Collect data on hooking times for turtles, bycatch and directed catch using hook timers & time depth recorders.

**Notes:**
The control hook was a 25° - 30° offset “J” hook and the control bait was squid.  Treatments were non offset 18/0 circle hook with squid bait, 10° offset 18/0 circle hook with mackerel bait, 10° offset 20/0 circle hook with mackerel bait, and non offset 10/0 Japanese tuna hook with mackerel bait. Data was also collected on hooking times and depths for target and bycatch species using hook timers and time depth recorders.

## 2003 ExperimentsTuna Sets

- Control
- 10° offset 16/0 circle hook with squid
- Treatment
- 18/0 non offset 18/0 circle hook with squid

**Notes:**
The control hook for tuna directed fishing sets was a 10° offset 16/0 circle hook and the control bait was squid and the treatment hook was a non offset 18/0 circle hook and the treatment bait was squid. 

## Hook Designs

- 9/0 J Hook

- 10/0 J Tuna Hook

- 16/0 Circle Hook

- 18/0 Circle Hook

- 20/0 Circle Hook

**Notes:**
Control and treatment hooks designs tested. 

## Experimental Design

- Set Configuration

- Control: 9/0 J Hook
-               25-30 Deg. Offset
-               w/ Squid Bait

- Treatments:
- Experimental Hooks
- Experimental Baits

**Notes:**
The experimental design was to evaluate the treatment hooks and baits using a randomized block design alternating control hooks and experimental hooks and bait along the entire set. Bait types (ie squid or mackerel) were not mixed on a set.  

## Fishing Effort

- 2001
- Eight vessels
- 186 sets
- 164,429 hooks
- 2002
- Thirteen vessels
- 489 sets
- 427,385 hooks
- 2003
- Eleven vessels
- 539 sets
- 578,050 hooks

**Notes:**
In 2001 eight commercial pelagic longline vessels made 186 sets fishing 164,429 hooks.  In 2002 thirteen vessels made 489 sets fishing 427,385 hooks, and in 2003 eleven vessels made 539 sets fishing 578,050 hooks. 

## Turtle Interactions

- 2001
- 142 loggerheads
- 77 leatherbacks
- 2002
- 100 loggerheads
- 158 leatherbacks
- 2003
- 92 loggerheads
- 79 Leatherbacks
- 1 Olive ridley

**Notes:**
There were 142 loggerhead and 77 leatherback caught in 2001, 100 loggerheads and 158 leatherbacks in 2002, and 92 loggerhead, 79 leatherbacks, and 1 olive ridley in 2003. 

## 2001 Results

- Blue-dyed Squid bait – no significant effect
- Move branch line 20 fathoms away from buoy - no significant effect for loggerheads
- 	increased catch of leatherbacks
- Daylight soak time – significant effect for *Caretta*

**Notes:**
Analysis of the data collected in 2001 indicated that there was no significant effect of blue dyed squid on turtle capture rates and that there was an increase capture rate for leatherback turtles on the hooks placed 20 fathoms from floats. A general linear model indicated that daylight hook soak time (the amount of time the hooks are in the water during daylight hours) was the only variable which effected loggerhead turtle capture rates, but there was no effect of daylight soak time for leatherback turtle captures. 

## Loggerhead Catch by Daylight Soak-time

- Hours after sunrise

- Catch per 1000 hooks

**Notes:**
Loggerhead cpue increases significantly with increased daylight hook soak time indicating that loggerhead interaction with longline gear in the NED is a daytime interaction. 

## 2002 Results

- Reduce daylight hook soak time – Not significant
- 18/0 circle hooks – Significant reduction loggerheads and leatherbacks
- Squid bait – decrease in swordfish, increase in tuna
- Mackerel bait - increase in swordfish, decrease in tuna
- Mackerel bait – Significant reduction loggerheads and leatherbacks, increase in swordfish, decrease in tuna

**Notes:**
Logistic regression models indicated that daylight soak time was not a significant variable in determining turtle interactions with longline gear.  18/0 circle hooks were found to significantly reduce both loggerhead and leatherback interactions when compared to J hooks.  18/0 circle hooks with squid bait reduced swordfish catch, but increased tuna catch.  18/0 circle hooks with mackerel bait had the highest reduction in loggerhead turtle interactions and increased swordfish catch, but decreased tuna catch.  J hooks with mackerel bait significantly reduced both loggerhead and leatherback interactions, increased swordfish catch, and reduced tuna catch. 

## Loggerhead Turtle CPUE

- Catch per 1,000 hooks

**Notes:**
Circle hooks with squid bait reduced loggerhead catch by 86% (CI= 73%-93% p<0.0001), mackerel bait with “J” hooks reduced loggerhead catch by 71% (CI = 42%-86%, p=0.0005), and circle hooks with mackerel bait reduced loggerhead catch by 90% (CI= 70%-97%, p<0.0001). 

## Leatherback Turtle CPUE

- Catch per 1,000 hooks

**Notes:**
Circle hooks with squid bait reduced leatherback catch by 57% (CI=34%-72%,P<0.0001), “J” hooks with mackerel bait reduced leatherback catch by 66% (CI=37%-81%, p = 0.0006), and circle hooks with mackerel bait reduced leatherback catch by 65% (CI=36%-81%, p=0.0006). 

## Swordfish CPUE

- Kilograms per 1,000 hooks

**Notes:**
Circle hooks with squid bait reduced swordfish catch by 29% (10° offset) and 33% (non offset) ( CI=14%-44%, p=0.0002 and 19%-46%, p<0.0001), “J” hooks with mackerel bait increased swordfish catch by 63% (CI= 46-81%, p<0.0001), and circle hooks with mackerel bait increased swordfish catch by 30% (CI = 14%-46%, p =0.0002).

## Bigeye Tuna CPUE

- Kilograms per 1,000 hooks

**Notes:**
Circle hooks with squid bait had a nominal increase in tuna catch of 26%. Mackerel bait reduced tuna catch by 81% (CI = 49% - 100%, p<0.0001) on circle hooks and 90%, CI = 58%-100%, p<0.0001) on “J” hooks. 

## Turtle Catch by Temperature

- Temperature (F)

- Catch per 1000 hooks

- J hooks

**Notes:**
Both loggerhead and leatherback turtle catch rates varied with the surface water temperature. There was a dramatic increase in loggerhead catch rates for water temperature over 72 degrees (F).  There was also an increase in leatherback turtle catch rates for water temperatures over 68 degrees (F).  This data indicates that turtle interaction rates can be reduced by fishing in cooler water temperatures. 

## Average Swordfish Weight by Temperature

- Average dressed weight (lbs)

- Temperature (F)

**Notes:**
The effect of surface water temperatures was the reverse for swordfish catch by weight.  The average dressed weight increased with cooler water temperatures (below 68 degrees (F).  

## Cold Water..........Big Fish! Fewer Turtles!

**Notes:**
This data indicates that a fishing water temperatures below 68 degrees (F) can significantly reduce loggerhead turtle interactions while increasing target catch rates. 

## 2003 Results

- 18/0 (non offset) circle hooks with squid bait Significant reduction loggerheads and leatherbacks, decreased swordfish catch, increased tuna catch
- 18/0 (10° offset) circle hooks with mackerel bait
- 	Significant reduction loggerheads and leatherbacks, increased swordfish catch, decreased tuna catch
- 20/0 (10° offset) circle hooks with mackerel bait
- 	Significant reduction loggerheads and leatherbacks, increased swordfish catch, decreased tuna catch

**Notes:**
The 18/0 non offset circle hooks with squid bait had significant reductions in loggerhead and leatherback catch when compared to the control “J” hook and squid bait, and an increased tuna catch, but had a significant reduction in swordfish catch.  The 18/0 10° offset circle hook with mackerel bait also had a significant reduction in catch of loggerhead and leatherback turtles compared to the control hook and bait and an increase in swordfish catch, but a significant decrease in tuna catch.  The 20/0 10° offset circle hook also had a significant reduction in loggerhead and leatherback catch, a slight increase in swordfish catch and a significant decrease in tuna catch. 

## Loggerhead Turtle CPUE

- Catch per 1,000 hooks

**Notes:**
18/0 (non offset) circle hooks with squid bait reduced loggerhead catch by 64% (CI = 37% - 80%  p = 0.0002), 18/0 (10° offset) circle hooks with mackerel bait reduced loggerhead catch by 89% (CI = 76%-95% p <0.0001) and 20/0 (10° offset) circle hooks with mackerel bait reduced loggerhead catch by 91% CI = 77%-96% p=<0.001). 

## Leatherback Turtle CPUE

- Catch per 1,000 hooks

**Notes:**
18/0 (non offset) circle hooks with squid bait reduced leatherback catch by 90% (CI = 66%-97% p<0.0001), 18/0 (10° offset) circle hooks with mackerel bait reduced leatherback catch by 56% (CI = 22%-76% p=0.0043), and 20/0 (10° offset) circle hooks reduced leatherback catch by 72% (CI = 42%-86% p=0.0002).  

## Swordfish CPUE

- Kilograms per 1,000 hooks

**Notes:**
18/0 (non offset) circle hooks with squid bait reduced swordfish catch by 29% (CI = 21%-36%). 18/0 (10° offset) circle hooks with mackerel bait increased swordfish catch by 12% and 20/0 (10° offset) circle hooks increased swordfish catch by 8%. 

## Bigeye Tuna CPUE

- Kilograms per 1,000 hooks

**Notes:**
18/0 (non offset) circle hooks with squid bait increased bigeye tuna catch by 20%, 18/0 (10° offset) circle hooks with mackerel bait decreased bigeye tuna catch by 83% (CI = 56%-100%) and 20/0 (10° offset) circle hooks with mackerel bait decreased bigeye tuna catch by 90% (CI = 62%-100%).

## Loggerhead Turtle CPUEPooled Data 2002 & 2003

- Catch per 1,000 hooks

**Notes:**
18/0 circle hooks with squid bait reduced loggerhead CPUE by 74% (CI = 58%-84%),  and 18/0 circle hooks with mackerel bait reduced loggerhead CPUE by 91% (CI = 82%-95%) for pooled data from 2002 and 2003. 

## Leatherback Turtle CPUEPooled Data 2002 & 2003

- Catch per 1,000 hooks

**Notes:**
The 18/0 circle hook with squid bait reduced leatherback CPUE by 75% (CI = 57%-86%) and the 18/0 circle hook with mackerel bait reduced leatherback CPUE by 67% (CI = 51%-78%) for 2002 and 2003 pooled data. 

## Tuna Directed Research Results

- Sample size is too small to determine effect, but preliminary numbers indicate reductions in both loggerhead and leatherback turtles with 18/0 circle hooks compared to 16/0 circle hooks.  Bigeye tuna catches were similar and there was a slight increase in yellowfin tuna catch with 18/0 circle hooks versus 16/0 circle hooks

##  Effect of Hook Size on Ingestion of Hooks by Loggerhead Sea Turtles 

- John W. Watson, Bret D. Hataway, and Charles E. Bergmann
- June, 2003

## Squid Bait Rigging

**Notes:**
Squid baiting method used in the experiments. Squid bait was the primary bait used in the experiments and was used on all hook types.  Squid used in the experiments were 150 to 250 gram weight. 

The experimental procedure was to present turtles a baited hook. The turtle response was recorded by an observer as four categories. The categories were: 
1. Did not take the hook into mouth.
2. Took the hook partially into mouth.
3. Took the hook fully into mouth. 
4. Attempted to swallow the hook.

Turtles were observed carefully by the researchers and once the hook was fully in the mouth and the turtle continued to swallow the bait, the hook and bait were pulled out of the mouth. Turtles were not allowed to actually swallow the hook. 

## Effect of Hook Width on Ingestion of Hooks by Loggerhead Turtles (40-60 cm Length)

- Hook Width

- Percent

- n=21           n=24             n=40            n=20

**Notes:**
Hook size had significant effect on the ingestion of hooks by loggerhead turtles between 40 and 60 cm in length. Ingestion of hooks and impact of associated leader material on loggerhead sea turtles is the most significant cause of mortality of the turtles which are incidentally captured by pelagic longline fishing gear.  The predominant hooks used in pelagic longline fisheries are less than 51 mm in width. Using hooks larger than 51 mm in width has the potential to significantly reduce mortality of loggerhead sea turtles incidentally captured by pelagic longline fisheries. 

## Summary of Logistic Regression Analysison Hook Swallowing Attempts

**Notes:**
Logistic modeling focused on the variables turtle size (mm), hook width (mm), and hook length (mm) as predictors of swallowing attempt. The terms turtle size and hook width are significant (p=0.0196 and p-0.0005, respectively) and hook length is a marginally significant (p=0.0772) predictor. This suggests that swallowing attempt should be looked at as a function of these three variables simultaneously.  
As expected, the model suggests that the probability of swallowing increases with (increasing) turtle size and decreases with (increasing) hook width and hook length. The table gives the coefficients, standard errors, and odds ratios, and 90% confidence intervals for each variable. 
The odds of swallowing increases by a multiplicative factor of 1.5% with one mm increase in turtle size. This means that the odds of swallowing increase by 25% with 15 mm increase in turtle size, by 50% with 27 mm increase in turtle size, and the odds doubles with 47 mm increase in turtle size. 
The odds of swallowing decreases by a multiplicative factor of 14.5% with one mm increase in hook width. This means that the odds of swallowing decrease by 37.5% with 3 mm increase in hook width, by 67% with 7 mm increase in hook width, and by 85% with 12 mm increase in hook width.
The odds of swallowing decrease by a multiplicative factor of 4.2% with one mmt increase in hook length. This means that the odds of swallowing decrease by 19% with 5 mm increase in hook length, by 35% with 10 mm increase in hook length, and 50% by 16 mm increase in hook length. 
Caution should be exercised in extrapolating beyond the ranges considered here for the predictors. 

## Hook Dimensions

| Hook Type | Hook Width | Hook Length |
| --- | --- | --- |
| 9/0 J  | 41 mm | 78 mm |
| 9/0 Tuna | 33 mm | 78 mm |
| 10/0 Tuna | 38 mm | 86 mm |
| 11/0 J | 51 mm | 98 mm |
| 16/0 Circle | 51 mm | 73 mm |
| 11/0 MJ | 56 mm | 86 mm |
| 18/0 Circle | 57 mm | 86 mm |
| 12/0 J | 57 mm  | 111 mm |
| 14/0 J | 63 mm | 130 mm |
| 20/0 Circle | 63 mm | 100 mm |

**Notes:**
Length and widths of hook types evaluated. 

## Pelagic longline Captains, Crews, and Owners
Blue Water Fishermen’s Assoc.
NOAA /Johnson Control Fisheries Observers
ARC
Lingren Pitman
Charlie Bergmann, Myrto Argyropoulou, Dennis Lee, Cheryl Brown, Larry Beerkircher, Lesley Stokes, Lisa Belskis, Dominy Hataway, Nick Hopkins, Lionel LaForce, Ron Rinaldo, Sari Karaly, Steve Myers, Ad Hoc advisory group 
Bill Hogarth

- Blue Water Fishermen’s Assoc.
- NOAA /Johnson Control Fisheries Observers
- ARC
- Lingren Pitman
- Charlie Bergmann, Myrto Argyropoulou, Dennis Lee, Cheryl Brown, Larry Beerkircher, Lesley Stokes, Lisa Belskis, Dominy Hataway, Nick Hopkins, Lionel LaForce, Ron Rinaldo, Sari Karaly, Steve Myers, Ad Hoc advisory group
- Bill Hogarth

**ACKNOWLEDGMENTS**

**Notes:**
This success of this research is due to the hard work and dedication of many individuals within the fishing industry and NOAA Fisheries. The principal investigators would like to give special recognition to the vessel captains, crews, owners, and managers from Bluewater Fishermen’s Association who’s expertise and efforts were invaluable. We would also like to especially thank the NOAA Fisheries observers who “go the extra mile” in collecting enormous amounts of quality data at sea and are the pulse of the research. We would like to thank Aquatic Research Conservation (ARC) for their tireless efforts in developing and modifying turtle release gear used in the experiments and to Lingren Pittman for developing the hook designs used in the experiments. A very special thanks to Charlie Bergmann, Myrto Argyropoulou, Dennis Lee, Cheryl Brown, Larry Beerkircher, Lesley Stokes, Lisa Belskis, Dominy Hataway, Lionel LaForce, Nick Hopkins, Ron Rinaldo, Sari Karaly, Steve Meyers, and the members of the longline mitigation research ad hoc advisory group for their extraordinary efforts. And finally our sincere appreciation to Bill Hogarth for his vision in developing this research program and his unfailing support.