Final Report to the VMRC and RFAB
Project Title: Establishment of a Chesapeake Bay Trophic Interaction Laboratory Services Program Report Number: 5 Principal Investigators: Christopher F. Bonzek, Dr. Robert J. Latour, Debra J. Parthree Period of Performance: 1 June 2004 to 1 June 2005 Award Number: RF 04-09 Funding Total: $121,919 ($95,000 VMRC, $26,919 VIMS) Introduction: Fisheries researchers and managers in the Chesapeake Bay region are developing multispecies management plans for commercially, recreationally, and ecologically important species. Both the Chesapeake 2000 (C2K) agreement and the recently completed regional Fisheries Ecosystem Plan (FEP) commit the states of Maryland and Virginia to incorporating an ecosystem-based approach into fisheries management. A principal requirement of multispecies fisheries assessment models is well-quantified estimates of predator-prey relationships (Latour et al. 2003). Trophic interactions among populations are typically elucidated through the analysis of stomach contents. It must be recognized, however, that such interactions vary according to temporal and spatial scales. Therefore, to adequately characterize these interactions within an ecosystem, an extensive database of fish diet composition information is needed. Further, given that increased survival in the early life history stages may ultimately improve the year-class strength of a fish population (Boynton et al., 1981), consideration of young-of-the year (YOY) and juvenile fish diets is particularly important. The goal of this project is to provide fisheries researchers and managers with an integrated trophic interations database that can be used to support the development of ecosystem-based fisheries assessment models. To meet that goal, the following objectives are established: 
Continue development of a network of collaborating researchers in the Chesapeake Bay region to collect fish stomach samples and associated environmental data.
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Construct a thorough fish diet composition database encompassing an array of species, locations/habitats, seasons, and age-classes throughout the Chesapeake Bay region.
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To ensure that our database reflects adequate temporal and spatial scales, samples and associated environmental data will be acquired from a client network of research projects across the bay and near-coastal region. Participation by Virginia Institute of Marine Science (VIMS) surveys will include that of the juvenile fish and blue crab trawl survey, the juvenile striped bass and bluefish seine surveys, and the newly established seagrass trammel net survey. Maryland Department of Natural Resources (MDNR) participation will include that of the juvenile striped bass seine survey, the adult striped bass creel survey, and adult spawning stock survey. Participation by the United States Fish and Wildlife Service (USFWS) near-coastal winter striped bass tagging survey (SEAMAP) is also anticipated.
Accomplishments and Benefits: Goals for the CTILS program were established and successfully achieved in each quarter for the 2004/2005 funding year. The network of collaborators grew to include seven fish surveys operating in the Chesapeake Bay vicinity (Figures 1 and 2). These surveys represent various and unique habitats throughout the Chesapeake Bay upon which a more complete understanding of trophic interactions among fish populations can be obtained. In the first quarter, five surveys from Maryland and Virginia provided samples to the CTILS program: the MDNR creel survey, the VIMS juvenile trawl survey, the VIMS trammel net survey, the VIMS juvenile bluefish seine survey, and the VIMS juvenile striped bass seine survey. The MDNR adult striped bass stomachs (54 stomachs) and the stomachs from the VIMS juvenile trawl from March through June (730 stomachs) were processed and analyzed. In the second quarter, the VIMS juvenile trawl survey, the MDNR juvenile striped bass seine survey, and the VIMS trammel net survey provided samples. The VIMS trammel net survey alone provided 925 stomachs from 24 species. Spot (Leiostomus xanthurus), Atlantic croaker (Micropogonias undulatus), and striped bass (Morone saxatilis) comprised 73% of the samples. Approximately 650 stomach samples were analyzed including 339 samples from the VIMS trammel net survey, 97 from the VIMS striped bass juvenile seine survey, and 187 from the VIMS bluefish juvenile seine survey. In the third quarter, two surveys provided samples to the CTILS program. A new client, North Carolina Division of Marine Fisheries (NCDMF) of the United States Fish and Wildlife Service (USFWS) provided a total of 214 stomach samples and whole fish from the annual winter tagging cruise aboard the R/V Oregon II off the coast of southeast Virginia and northeast North Carolina. The VIMS juvenile trawl survey continued to provide a subsample of their catch each month from the James, York, and Rappahannock Rivers. Approximately 850 stomach samples were analyzed including 168 samples from the MDNR juvenile striped bass seine survey, 159 samples from the VIMS trammel net survey, 330 samples from the VIMS juvenile trawl survey, and 186 samples from the NCDMF winter tagging cruise. Priorities for this quarter were based on specific requests from participating surveys.
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Figure 1. Potential locations sampled by various VIMS and MDNR monitoring surveys. Exact locations, chosen at random, may change each month. The Chesapeake Bay main stem is surveyed by the MDNR adult striped bass creel survey as well as the Chesapeake Bay Multispecies Monitoring and Assessment Program (ChesMMAP) at VIMS.
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Figure 2. Sampling locations for the USFWS Winter Tagging Cruise operated by the North Carolina Division of Marine Fisheries (NCDMF).
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In the fourth quarter, the VIMS juvenile trawl survey continued to provide a subsample of their catch each month from the James, York, and Rappahannock Rivers. In addition, the VIMS trammel net survey provided 95 samples from a blue crab enhancement project that involved releasing tagged juvenile crabs into the environment. The majority of the these samples came from the York River Catlett Island sites, a part of the Chesapeake Bay National Estuarine Research Reserve in Virginia (CBNERRVA). A total of approximately 700 samples were examined including 460 samples from the VIMS juvenile trawl survey, 106 samples from the VIMS juvenile striped bass seine survey, 27 samples from the VIMS trammel net survey, 95 samples from the blue crab enhancement study collaborating with the trammel net survey, and 12 samples from the VIMS juvenile bluefish seine survey. A priority for this quarter was to present a poster at the Chesapeake Bay Stock Assessment Committee (CBSAC) symposium in Bowie, Maryland. The poster was entitled “Diet of striped bass (Morone saxatilis) compared among seven surveys in the vicinity of Chesapeake Bay, USA, 2003-2005. Accordingly, a large proportion of the stomachs processed were from striped bass. Purchases for the CTILS program for the year included field and laboratory supplies (Table 1) In addition, money was spent on the transport of samples from the study area to the VIMS trophic ecology laboratory.
Table 1. Purchases for the CTILS program in the 2004/2005 VMRC funding year. stomach sample bags whirl paks scissors gloves 5-gallon buckets
Normalin preservative measuring board calipers camera mini tripod
glassware forceps ice chests waterproof paper
The CTILS program continually publicizes the CTILS program as a laboratory service and maintains communication with both potential and established partners. A website was developed to demonstrate the program’s services and can be accessed at www.vims.fisheries.edu/ctils. Analysis Of the 3852 stomach samples processed, the VIMS juvenile trawl survey provided 1772 (Part I), the MDNR juvenile striped bass seine survey provided 594 (Part II), the VIMS trammel net survey provided 525 (Part III), the VIMS juvenile bluefish seine survey provided 245 (Part VI), the MDNR creel and spawning stock surveys provided 236 (Part V), the USFWS winter tagging cruise provided 222 (Part VI), the VIMS juvenile striped bass seine survey provided 209 (Part VII), and the VIMS crab enhancement survey working in collaboration with the trammel net survey provided 95 (Part VIII).
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Part I VIMS Juvenile Fish and Blue Crab Trawl Survey An analysis of 272 striped bass captured by the VIMS juvenile trawl survey revealed slight differences in the diet between fish foraging in the James, Rappahannock, and York Rivers (Figure 3). Bay anchovy appeared to be the primary prey type for fish in the Rappahannock River, while Atlantic menhaden dominated the diet of fish in the York River. Anchovy and menhaden appeared equally important in the diet of fish foraging in the James River. Figure 3. Diet by weight of striped bass captured by trawl in the James, Rappahannock, and York Rivers in the Chesapeake Bay, Virginia, 2004.
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Summer flounder is also an important predator in the Virginia tributaries. Of 235 samples processed, slight differences were revealed again (Figure 4). Mysids were the most important prey of flounder in the James River and bay anchovy dominated the diet of fish in the Rappahannock River. Weakfish and bay anchovy were equally important in the diet of those fish foraging in the York River. Figure 4. Diet by weight of summer flounder captured by trawl in the James, Rappahannock, and York Rivers in the Chesapeake Bay, Virginia, 2004.
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In an analysis of 406 weakfish captured by the same survey, the weakfish diets appeared to show similarities to both the striped bass and the summer flounder diets (Figure 5). While mysids were slightly dominant over bay anchovy in the diet of weakfish foraging in the James River, Atlantic menhaden dominated similarly over bay anchovy in the Rappahannock River. In the James River, bay anchovy was slightly more important than mysids and menhaden as well as other fish.
Figure 5. Diet by weight of weakfish captured by trawl in the James, Rappahannock, and York Rivers in the Chesapeake Bay, Virginia, 2004.
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Part II. MDNR Juvenile Striped Bass Seine Survey For the Maryland age-0 striped bass samples, salinity appeared to explain the diversity in diet between the five river systems studied (Figure 6). Variations in diet of age-0 striped bass are most often attributable to salinity (Markle and Grant, 1970; Boynton et al., 1981) and spatial variations where salinity was significantly different among sites (Jordan et al., 2003). The dominant prey types encountered in the stomachs of the fish from each river are displayed with percent weight composition above each salinity bar for 2003 and 2004. Figure 6. Dominant prey types by weight found in the diet of age-0 striped bass captured by seine from Maryland river systems of Chesapeake Bay with varying salinity, August 2003 and August 2004.
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Part III. VIMS Trammel Net Survey The purpose of the trammel net survey at VIMS is to quantify the impacts of predation, particularly by striped bass, on the juvenile blue crab population in seagrass habitat. A monthly analysis, from April to November 2004, of striped bass diet revealed blue crabs as the primary prey in eight months out of the ten-month span (Figure 7). Exceptions were in April when polychaetes dominated and in August when fish were the primary prey. In November, other crabs and shrimp were nearly as important as blue crabs. Figure 7. Monthly diet by weight of striped bass captured by trammel net in seagrass beds of Chesapeake Bay, 2004.
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Atlantic croaker were captured in large numbers by the trammel net survey. The croaker did not heavily exploit blue crabs, and a monthly comparison from April to September 2004 revealed only slight diet shifts (Figure 8). Clams were the primary prey in April and June and were the primary viable prey type in May, besides miscellaneous and unidentified material such as eelgrass and marsh substrate. Polychaetes dominated the diet in August and September; however, crabs and shrimp were nearly as important as polychaetes in the diet in September. Figure 8. Monthly diet by weight of Atlantic croaker captured by trammel net in seagrass beds of Chesapeake Bay, 2004.
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Smaller numbers of spot, white perch, silver perch, bluefish, summer flounder, and weakfish captured in the seagrass beds were analyzed (Figure 9). Grass shrimp were important in the diets of white perch, silver perch, and summer flounder. Of nearly equal importance to grass shrimp in the summer flounder diet was sand shrimp. Spot fed primarily upon clams, and bluefish ate mostly bay anchovy. Blue crabs were exploited about as equally as bay anchovy by weakfish. Figure 9. Diet by weight of six fish species captured by trammel net in seagrass beds of Chesapeake Bay, April to November 2004.
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Part IV. VIMS Juvenile Bluefish Seine Survey A comparison of the diet of six juvenile fish species, including two size classes each of Atlantic croaker and Atlantic needlefish, captured by seine on the Eastern Shore and Southside Chesapeake Bay revealed some similarities and some differences in primary prey types for each species (Figure 10). The two size classes of Atlantic croaker consumed vastly different diets. The smaller fish (18-42 mm) ate almost entirely mysids, and the larger fish (116-303 mm) consumed almost exclusively Atlantic silversides. Mysids were also the primary prey of silver perch; and Atlantic silversides, along with anchovies, bluefish, and striped killifish, dominated the diet of the larger Atlantic needlefish (200-473 mm). The smaller Atlantic needlefish (34-197) ate mostly unidentified fish along with white mullet and insects. Summer flounder also consumed mostly unidentified fish. Bluefish consumed anchovies and white mullet, and kingfish preyed primarily upon crabs and shrimp.
Figure 10. Diet by weight of fish species collected by seine on the Eastern Shore and Southside Chesapeake Bay, VA, June through September 2004.
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Part V. MDNR Creel Survey Adult striped bass were sampled for diet analysis during the sportfishing season in the Maryland Chesapeake Bay main stem from 2003 to 2005. The analysis clearly indicates heavy exploitation of Atlantic menhaden by large striped bass in this region (Figure 11). Figure 11. Diet by weight composition of adult striped bass captured by hook and line in the Chesapeake Bay, Maryland, 2003, 2004, and 2005.
Part VI. USFWS Winter Tagging Cruise An analysis of the small sample of predatory species captured by the winter tagging cruise in the nearshore North Carolina and Virginia waters reveals a nearly exclusive diet of bay anchovy as the primary prey type for summer flounder, Atlantic croaker, and weakfish (Figure 12). Striped bass also rely heavily on bay anchovy as well as Atlantic menhaden. Spotted hake fed primarily on shrimp in addition to smaller amounts of polychaetes and bay anchovy. Figure 12. Diet by weight of fish species captured by trawl in the North Carolina and Virginia nearshore waters, 25 January to 2 February, 2005.
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Part VII. VIMS Juvenile Striped Bass Seine Survey A comparison of the diet of five juvenile fish species, including two size classes of white perch, captured by seine in the James, York, and Rappahannock Rivers revealed different primary prey types for each species, although all of the species foraged on a variety of prey (Figure 13). Atlantic croaker fed primarily on polychaetes, but also utilized clams in their diet. Clams were the most important prey for blue catfish, although nearly equally important were insects. Insects were also important in the diet of white perch (80-204 mm), along with crabs and shrimp, and amphipods. Smaller white perch (38-80 mm) fed primarily on zooplankton (copepods and cladocerans), amphipods, mysids, and polychaetes. The striped bass diet was most similar to the larger size white perch diet, consisting primarily of amphipods and crabs and shrimp. Weakfish preyed mostly upon fish and mysids.
Figure 13. Diet by weight of fish species collected by seine in the James, York, and Rappahannock Rivers, VA, July through September 2004.
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Part VIII. Crab Enhancement Study in collaboration with the VIMS Trammel Net Survey The majority of the samples collected from the crab enhancement study were Atlantic croaker from Catlett Island east and west sites. At the east site, the main prey type was crabs (primarily blue crabs and grass shrimp) and the main prey type at the west site was razor clams (Tagelus plebeius) (Figure 14). Important prey at both sites were polychaetes (clam worms, bloodworms, and bamboo worms). Figure 14. Diet by weight of Atlantic croaker captured by trammel net at Catlett Island, York River, Virginia, June-July 2004. 100% other invertebrates
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The disparity and diversity in diet composition shown in these analyses emphasize the importance of collecting diet data from a variety of surveys, which expands the spatial and temporal coverage as well as the size range of fish sampled. Combining data from a variety of surveys provides a comprehensive diet composition database, and therefore, a more reliable parameterization of multispecies fisheries assessment models. The above representations are examples of the type of analyses which can be performed using diet data of Chesapeake Bay fishes. As the database grows, much more detailed diet information will be generated. Since its inception, CTILS has processed nearly 4000 stomach samples (Table 2). The majority of the stomachs came from striped bass, an important predator in the Bay, and Atlantic croaker, an extremely abundant species.
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Table 2. Fish species, number of stomachs, and percent of total processed by the CTILS program from its inception in June 2003 to June 2005. Species Morone saxatilis Micropogonias undulatus Paralichthys dentatus Ictalurus furcatus Cynoscion regalis Bairdiella chrysoura Menticirrhus spp. Strongylura marina Leiostomus xanthurus Pomatomus saltatrix Alosa pseudoharengus Alosa aestivalis Morone americana Anchoa mitchilli Urophycis regia Rhinoptera bonasus Cynoscion nebulosus Sphyraena borealis Sciaenops ocellatus Tylosurus crocodilus Archosargus probatocephalus Perca flavescens Brevoortia tyrannus Pogonias cromis Dasyatis americana Synodus foetens Orthopristis chrysoptera Ictalurus catus Dasyatis sabina TOTAL
Common name striped bass Atlantic croaker summer flounder blue catfish weakfish silver perch kingfish spp. Atlantic needlefish spot bluefish alewife blueback herring white perch Bay anchovy spotted hake cownose ray spotted seatrout northern sennet red drum houndfish sheepshead yellow perch Atlantic menhaden black drum southern stingray inshore lizardfish pigfish white catfish Atlantic stingray
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Total Percent of Total 1539 39.95 820 21.29 329 8.54 298 7.74 248 6.44 122 3.17 86 2.23 74 1.92 56 1.45 54 1.40 45 1.17 40 1.04 32 0.83 25 0.65 22 0.57 15 0.39 14 0.36 9 0.23 7 0.18 3 0.08 3 0.08 3 0.08 2 0.05 1 0.03 1 0.03 1 0.03 1 0.03 1 0.03 1 0.03 3852 100.00
Individual analyses of these data and results are detailed in formal reports to the participating surveys and are available upon request. The database created by CTILS will be incorporated into the Chesapeake Bay Ecopath with Ecosim (EwE) model as well as several multispecies bioenergtics models (Latour et al. 2003) currently under development by our research group. From these models, sound management decisions can be made based upon a more complete understanding of the population dynamics and interactions of commercially and recreationally exploited fish stocks. All diet and related field data will become a part of a regional library and will be identifiable as to survey and/or investigator. Any publications that result from shared samples will either be joint publications with those who provide samples, or the partners will be given appropriate acknowledgement according to the level of participation. In addition, these publications will formally acknowledge Virginia Marine Resources Commission’s Recreational Fishing Advisory Board.
Literature Cited Boynton, W.R., T.T. Polgar, and H.H. Zion. 1981. Importance of juvenile striped bass food habits in the Potomac estuary. Transactions of the American Fisheries Society. 110:56-63. Jordan, R.C., D.V. Howe, T.P. Hurst, and F. Juanes. 2003. Feeding habits of age-0 striped bass, Morone saxatilis, in the mid-Hudson River estuary: Temporal, spatial, and ontogenetic variation. Estuaries. 26(6):1486-1493. Latour, R.J., M.J. Brush, and C.F. Bonzek. 2003. Toward ecosystem-based fisheries management; strategies for multispecies modeling and associated data requirements. Fisheries 28:10-22. Markle, D.F. and G.C. Grant. 1970. The summer food habits of young-of-the year striped bass in three Virginia rivers. Chesapeake Science. 11(1):50-54.
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