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MEMORANDUM Tetra Tech, Inc. 400 Red Brook Blvd., Suite 200 Owings Mills, MD 21117 phone 410 - 356 - 8993 fax 410 - 356 - 9005
DATE: February 1 8 , 2008 TO : Paul Shriner and Jan Matuszko, EPA FROM : Blaine Snyder, Henry Latimer, Ann Roseberry Lincoln , Kelly Meadows and Shari Goodwin SUBJECT: SEAMAP and Other Data Applicability to Other Coastal Settings Introduction In 2005 , Tetra Tech prepared a memorandum for EPA entitled “A Summary of Ichthyoplankton Presence and Abundance in the Gulf of Mexico, as Part of an Assessment of the Potential for Entrainment by Offshore Oil and Gas Facilities” ( DCN 9
- 5200; FDMS ID EPA
- HQ
- OW
- 2004
- 0002
- 1956[1]). In that memo (included in the rulemaking record for the Phase III rule) , the Southeast Area Monitoring and Assessment Program (SEAMAP) (Hanisko 2004) database was used to characterize ichthyoplankton (fish eggs and larvae) presence, composition, and density within the Gulf. Recently, EPA expressed interest in understanding how well the SEAMAP data/results translate to a c oastal setting (as opposed to open water) or if similar data exists for other coastal locations. Of particular interest to EPA is the relationship of ichthyoplankton density to water depth and how the SEAMAP conclusions translate to other coastal areas (particularly the California coast). Review of Data The 2005 memo presented a plot of average ichthyoplankton densities against depth at 10 meter intervals (copied here as Figure 6). General trends were similar between egg and larval fish densities. The den sities of both declined rapidly from 0 to 60 meters in depth. As depth increased past 60 meters, the decline in ichthyoplankton and egg densities was less pronounced.

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We also prepared a map of SEAMAP sampling locations (copied here as Appendix A) that c olor

coded sampling site location symbols to reflect ichthyoplankton density ranges (darker shades represented higher densities). The site density information, combined with bathymetry contour delineations, mirrored the results of ichthyoplankton density graphs, i.e., that density generally increased as depth decreases.

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Applicability of SEAMAP and Other Data EPA is interested in knowing how well the SEAMAP conclusions (e.g., relationship of ichthyoplankton density to water depth) translate to other coastal areas (particularly the California coast). Intuitively, it would not be prudent to simply assume the SEAMAP data/results could be applied to (or represent trends in) other coastal areas. For example, when comparing the Gulf o f Mexico to the California coast, there are notable differences in fish assemblages (species composition), water temperatures, currents, tides, and coastal zone morphology. It would be advisable to collect ichthyoplankton data from other coastal areas of i nterest and perform the same analysis that we applied to the SEAMAP data. Fortunately, Tetra Tech able to find a few literature sources that documented applicable research in other coastal areas (California, Oregon, and Washington). We also obtained ichthyoplankton density data for the Gulf of Maine. In addition, a study conducted in Great Britain further corroborates the statement that ichthyoplankton densities increase with decreasing depth. Auth et al. (2007) examined diel variation in the vertical dis tribution of ichthyoplankton from a point location off the Oregon Coast. Their sampling consisted of continuous oblique ichthyoplankton tows from a depth of 350 meters to the water’s surface. Their research documented that the vast majority (96%) of fish l arvae were present in the upper 100 meters of the water column. The authors stated that, “One implication from these findings is that sampling in the upper 100 meters of the water column should be sufficient to characterize pelagic summer ichthyoplankton abundances and distributions of the majority of fish taxa along the northeastern Pacific coast.” This particular paper (Auth et al. 2007) included a figure that summarized diel differences and in the proportion of total abundances for the dominant larval t axa (A = slender sole; B = scorpionfishes and rockfishes; C = northern lampfish; and D = lanternfish), copied here as Figure 2. This figure also summarized their abundances at depth intervals, and reflects the text conclusion that ichthyoplankton abundance is greatest at depths less than 100 meters (and perhaps further, abundances are greatest at depths less than 50 meters during night and early morning hours). Applicable research was also presented in Doyle (1992). This paper discusses the analysis of ichthyoplankton data collected off of the Washington, Oregon, and northern California coasts during the 1980s. Ten sampling cruises were completed over a period of seven years, and 125 sampling stations were visited during each cruise. Sampling consisted of oblique tows to a 200

- meter depth (or 5 meters from the bottom in water shallower than 200 meters) at each station. This research documented that most taxa of fish larvae occurred close to the coast (over the shelf and slope) and were absent or scarce in the deepest part of the oceanic zone. The author stated that, “This is true of the pelagic Engraulis mordax and the demersal hexagrammids, cottids, Ronquilus jordani , Cryptacanthodes aleutensis , and Ammodytes hexapterus . Adult populations of these species ar e essentially coastal. Some, such as Hexagrammos decagrammus , H. lagocephalus , Hemilepidotus spinosus , and Scorpaenichthys marmoratus , are most abundant close to shore, where they spawn from the intertidal zone to a maximum depth of 100 meters.” This paper (Doyle 1992) included a figure that summarized patterns of distribution for dominant larval fish taxa as grid squares on a coastal map (copied here as figures 7 and 8). The larval density figures reflect the text conclusion that most taxa of fish larvae (and highest densities) occur close to the Washington, Oregon, and northern California coasts (over the shelf and slope).

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Runge and Jones collected ichthyoplankton from May 2005 through June 2007 at five sampling locations in the Gulf of Maine. S ampling consisted of continuous oblique tows to a depth of five meters above the bottom. Samples were sorted in the laboratory and fish larvae were identified to the species level

. Tetra Tech combined the species data to obtain total larval densities for e ach sample, and averaged the samples by maximum depth, grouped into 15

- meter increments. Table 1 shows the number of samples obtained at each depth for each station. Figure A graphs the average densities versus the maximum tow depth (again grouped into 15

- meter increments), demonstrating that ichthyoplankton densities generally increase as depth decreases. Additionally, we summed the depth

- averaged densities to obtain a total average density for each station, and displayed the results on a map of the Gulf of Maine. Figure B shows the results: the greatest densities occur closest to the coast. Table 1. Number of ichthyoplankton samples collected at each station in specified depth ranges.

Lowest Tow Depth Stations

CT1 CT3 WB2 WB3 WB4 0 to <= 15 m 15 to <= 30 m 1 30 to <= 45 m 17 5 45 to <= 60 m 10 2 15 60 to <= 75 m 12 1 2 75 to <= 90 m 90 to <= 105 m 15 105 to <= 120 m 120 to <= 135 m 1 135 to <= 150 m 1

### 8 Figure A. Average ichthyoplankton density by to w depth. Runge and Jones data result from oblique tows from the ocean surface to approximately five meters from the bottom. Categories represent the lowest tow depths, grouped into 15
- meter increments.

Figure B. Average ichthyoplankton density at five sampling stations in the Gulf of Maine. Average total bottom to surface ichthyoplankton densities presented in number of larvae per cubic meter. Similar patterns hold in other areas of the world, as well. Fortier and Harris (1989) studied vertical ontogen etic fish larvae migrations at a station off Plymouth, UK, on the north coast of the Western English Channel. Constant

- volume samples were collected with a large

- volume pump

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system at discrete five

- meter depth intervals from 55 m to the surface. Their F igu re 6 (copied below) shows the vertical distribution of fish larvae by species, size class, and time of day. The authors note that “The vertical distribution of fish larvae varied little over the diel cycle but changed considerably during ontogeny.” Specifi cally, the post yolk

- sac larvae of all the species mo ved progressively deeper in the water column with growth. These findings suggest that larval densities do not decrease significantly between the surface and 55 m depth.

Conclusions The findings of the SEAMAP analysis for the Gulf of Mexico are generally supported by the cited papers from the Pacific and British coasts and the data from the Gulf of Maine, i.e., that ichthyoplankton densities increase as depth and distance from shore decrease, and tha t abundance is greatest at depths less than 100 meters.

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Literature Cited Auth, T.D., R.D. Brodeur, and K.M. Fisher. 2007. Diel variation in vertical distribution of an offshore ichthyoplankton community off the Oregon coast. Fisheries Bulletin 105:313

- 326. Doyle, M.J. 1992. Neustinic ichthyoplankton in the northern region of the California current ecosystem. CalCOFI Report, Vol. 33: 141

- 161. Fortier, Louis and Roger P. Harris. 1989. Optimal foraging and density

- dependent competition in marine fish larvae. Marine Ecology Progress Series 51: 19

- 33. Hanisko, David. 2004. Personal communication. NOAA. National Marine Fisheries Service, Paspagoula Laboratory, Mississippi. Personal comm. 2004. Runge, J.A. and R.J. Jones. PULSE: A Cooperative Partnership f or Coastal Ocean Ecosystem Monitoring in the Gulf of Maine. Award # NA16FL2452, Northeast Consortium. Data available online at http://www.cooa.unh.edu/data/boats/zooplankton/bongoNetsDensity/index.jsp

. Accessed on January 13, 2009.