Chesapeake Bay Trophic Interactions Laboratory Services (CTILS) (original) (raw)
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Transactions of the American Fisheries Society, 2011
Trophic studies of summer flounder Paralichthys dentatus have relied on traditional stomach content analyses to infer contributions of prey to species productivity. We applied both stable isotope and stomach content analyses to identify prey groups that are responsible for summer flounder productivity in lower Chesapeake Bay and to explore ontogenetic patterns in prey utilization. Summer flounder (total length = 138-682 mm; age = 0-11 years) were collected for stomach and tissue samples (liver, blood, and muscle) during spring-summer (May-July) and fall (November) of 2006 and 2007. Commonly consumed crustacean and fish prey species were also collected: mysid shrimp Neomysis americana, sevenspine bay shrimp Crangon septemspinosa, mantis shrimp Squilla empusa, bay anchovy Anchoa mitchilli, spotted hake Urophycis regia, and juvenile sciaenids. Analysis of the nitrogen stable isotope ratio (δ 15 N; ratio of 15 N to 14 N relative to a standard) revealed that crustaceans comprised the majority (72-100% on average) of the summer flounder diet except in spring 2006, when fish consumption was more dominant. Analysis of corresponding stomach contents indicated a lower contribution of crustacean prey. Based on isotopes, summer flounder tended to occupy the same trophic level as the prey fishes. The δ 15 N in all tissues exhibited a positive trend with body length, indicating that larger summer flounder fed at approximately one trophic level above smaller individuals; the positive trend also corresponded with increasing proportions of fish in summer flounder stomachs. Our stable isotope analysis indicates that growth and production of summer flounder in lower Chesapeake Bay are highly dependent on assimilation of mysid shrimp, sevenspine bay shrimp, and mantis shrimp-more so than previously expected based on stomach content research.
BACKGROUND The Chesapeake 2000 (C2K) Agreement commits regional jurisdictions to implement multispecies approaches to fisheries management. The potential for biological interactions and technical interactions within traditional single species management has motivated the development of multispecies approaches. Houde et al. (1998)1 reported the recommendations of a workshop to explore the utility and advisability of adopting multispecies approaches in Chesapeake Bay. An important conclusion of the workshop was the development of coordinated, baywide surveys to estimate key species abundances and to provide biological data on both economically and ecologically important species that are currently lacking (Houde et al. op. cit.). Since 1995, we have conducted research that seeks to provide information that will be needed to design a suitable baywide multispecies survey in support of C2K commitments. This research has several objectives that directly address issues relating to the desig...
2006
The lower Chesapeake Bay and coastal ocean of Virginia serve as an important nursery area for bluefish Pomatomus saltatrix. Describing the diet composition of young-of-the-year (hereafter, age-0) bluefish in this region is essential to support current Chesapeake Bay ecosystem modeling efforts and to contribute to the understanding of the foraging ecology of these fish along the U.S. Atlantic coast. The stomach contents of 404 age-0 bluefish collected from the lower Chesapeake Bay and adjacent coastal zone in 1999 and 2000 were examined as part of a diet composition study. Age-0 bluefish foraged primarily on bay anchovies Anchoa mitchilli, striped anchovies Anchoa hepsetus, and Atlantic silversides Menidia menidia. Other fishes such as striped bass Morone saxatilis, white perch Morone americana, Atlantic menhaden Brevoortia tyrannus, and bluefish were seasonally important. Crab zoea and megalope Callinectes spp. and amphipods Gammarus spp. were the most important invertebrate prey. A seasonal dietary shift from Atlantic silversides to anchovies was evident. Overall, small pelagic and littoral schooling fishes, particularly engraulids and atherinids, predominated in the diet of the age-0 bluefish collected for this study. Although the results presented here were similar to the diet composition of age-0 bluefish reported in previous studies, some notable differences were probably due to spatial and temporal differences in prey assemblages.
2010
II. To estimate the overall metabolic demand/consumption of fish-obligate breeding bird communities in order to parameterize current Chesapeake Bay ecosystem models III. To develop a novel, fishery independent tool for stock assessment of Atlantic menhaden and American shad by identifying diagnostic isotopic markers which will allow tracking of Atlantic population trends using feathers from sentinel bird species (e.g. Osprey). Summary of work performed: SPECIFIC PROJECT OBJECTIVES: 1) Quantify the complex relationships among temporal trends and geospatial patterns, and across multiple scales, using archival, long-term databases of the geographic distribution and abundance of avian predators and selected fishery resources in the Chesapeake Bay region (Chapter 1). 2) Complete a two-part retrospective analysis consisting of an analysis of stable isotopes from Bald Eagles and Osprey occupying the Chesapeake Bay circa 1850-2002 in order to estimate historical trends in the contribution of anadromous fishes, including American shad, to the diet of Osprey and Bald Eagles over very broad temporal scales. Feathers have been collected from the Smithsonian Institution (historical period) and active nests throughout Chesapeake Bay and its tidal tributaries (Chapter 2). 3) Use conventional energetics-based methods to estimate the overall metabolic demand and consumption of fishery resources for selected avian species in order to contribute to the parameterization of existing Chesapeake Bay ecosystem models (Chapters 3). 4) For most piscivorous birds comprehensive data on the composition and size distribution of fish prey are lacking. We stratified estimates of avian consumption according to fish species by compiling existing diet information for bird consumers and conducting avian diet studies for those species for which data are lacking (e.g. Osprey, Double-crested Cormorants, and Pelicans). Concurrent with avian diet studies, fishery hydroacoustic surveys were conducted to estimate available fish biomass and quantify the impact of local consumption by fish-eating birds (Chapter 4). 5) Develop and test novel, fishery independent stock assessment tool based on diagnostic stable isotope biomarkers (fatty acid signature analysis) for Atlantic menhaden and American shad in sentinel avian predators (Chapter 5).
Diet Composition and Feeding Habits of Common Fishes in Long Island Bays, New York
Northeastern Naturalist, 2011
Developing models in support of ecosystem-based management requires knowledge of trophic dynamics of ecologically important species. A paucity of data on these dynamics for Long Island fi nfi sh is hindering development of ecosystem models required by recent legislation. In this study, we analyzed stomach contents of common fi shes collected from Port Jefferson Harbor, Great South Bay, and Shinnecock Bay between May and October of 2007 and 2008. General diet composition was described by percent by number (%N), percent by weight (%W), percent frequency of occurrence (%O), and percent index of relative importance (%IRI) for seven species: Paralichthys dentatus (Summer Flounder), young-of-the-year (YOY) Pomatomus saltatrix (Bluefi sh), Prionotus evolans (Striped Searobin), Stenotomus chrysops (Scup), Scophthalmus aquosus (Windowpane Flounder), Raja eglanteria (Clearnose Skate), and Morone saxatilis (Striped Bass). Temporal diet composition was estimated for the consistently abundant YOY Bluefi sh, Summer Flounder, and Scup, where most n season > 25. Subsampling of large catches of YOY Bluefi sh and Scup led to investigation of diet composition by cluster sampling. Important prey included Crangon sp. (sand shrimp), Cancer irroratus (Rock Crab), and forage fi shes. Pseudopleuronectes americanus (Winter Flounder), once a common prey item in stomachs of piscivorous Long Island fi shes, contributed 6.7 %O and 1.6 %W to the diets of Summer Flounder, Striped Searobin, Striped Bass, and YOY Bluefi sh. These changes may be due to shifts in the abundance of prey items or changes in spatial overlap of predator and prey.
Chesapeake Bay Fisheries: Prospects for Multispecies Management and Sustainability
2006
Fishery resources in the Chesapeake Bay are currently managed as individual species. In this framework the potential effect of the harvest of a species on the ecosystem generally is ignored. However, the Chesapeake Bay supports a multispecies fishery that annually lands finfish and shellfish worth in excess of $100 Million. Over the past 25 years the average annual commercial landing has been approximately 250,000 metric tonnes. Although menhaden and blue crabs represent ninety-five percent, by weight, of the commercial catch in the Bay, statistics show that 59 other species are also caught. The recreational sector also accounts for a large and diverse catch. Furthermore, there have been significant changes in the nature of the fishery. Over the last one hundred years landings of oysters have diminished greatly, and in their place, landings of blue crab have risen dramatically. Over the same time period landings of anadromous fishes, such as American shad have declined. In contrast, landings of menhaden have risen so that its fishery now accounts for over 80%, by weight, of the total catch. The multispecies nature of the combined fisheries arises for both technical and biological reasons. Technical interactions, which arise when a fishery targets on one species but catches other species incidently as bycatch, are present in the Chesapeake Bay. For example, 45 species are taken in poundnet fisheries and 53 species are taken in gillnet fisheries. Technical interactions are important considerations in fisheries management as they may limit the ability to regulate overall rates of fishing mortality. Biological interactions, which arise when a targeted species is an important link in a food web, also occur in the Chesapeake Bay. For example the removal of top predators (striped bass, bluefish and weakfish) may have significant impacts on the dynamics of the planktivore species, and thus the plankton community itself. Additionally, harvests of blue crab, spot and croaker have the potential to influence energy and nutrient exchanges between the benthic and pelagic food webs. To address these multispecies interactions several new approaches to fisheries management have been developed. These approaches implicitly account for intra-specific interactions. Ultimately, these approaches may be more compatible philosophically with the ecosystem-level management of the Chesapeake Bay's other natural resources. We explored the need for and potential of multispecies approaches to the management of fisheries resources in the bay. The evidence suggests that adopting a multispecies approach would be advantageous. Many of the forces that lead to the adoption of multispecies management in other ecosystems are present in the Chesapeake, including concerns over extensive bycatches, and the presence of coupled population dynamics for several components of the ecosystem. We reviewed multispecies approaches employed elsewhere in the U.S. and worldwide. We identified several broad classes of approach. The most direct approaches were descriptive involving graphical or multivariate statistical approaches such as principal components analysis and state-space time series analysis. These approaches are suitable to identify the extent and importance of the multispecies character of a fishery, but may have limited utility for management. Other approaches are more mechanistic. Examples include closed-form, and simulation models of interacting species, and more holistic models of the entire system. We suggest that multispecies models addressing technical interactions, and those involving descriptive rather than mechanistic approaches are most likely to be successful in the near-term. However, several approaches such as simulation modeling and multispecies virtual population Multispecies Fisheries Approaches in the Chesapeake iv analysis seem unsuitable management tools for the Chesapeake Bay due to their high demand for data that is not currently available. New research, data collection and database development to correct these shortcomings are strongly recommended. Our review indicates that several factors currently preclude adopting a multispecies approach in the Chesapeake Bay. Specific areas that must be addressed, which would improve current single-species management and develop the capability to explore the application of multispecies approaches include the need for: < systematic information on catch and effort for exploited stocks, < fishery-independent estimates of abundance for principal species in the bay, < basic life history information, < detailed knowledge of species interactions (especially predator-prey relationships), < effects of habitat alteration, < detailed understanding of multispecies models. Adopting multispecies approaches to management would be a major shift away from traditional single species management and a major step toward fulfilling the ecosystem management goal of the Bay Program. We are not ready for this step today, but addressing the identified deficiencies will prepare us for multispecies management in the future.
Estuaries, 1987
Examination of gut contents of the northern pipefish, Syngnathus fuscus, revealed that gammarid amphipods, caprellid amphipods, isopods, and calanoid copepods were the dominant food items during the sevenmonth study period. Gammarus mucronatus, calanoid copepods, and Erichsonella attenuata were the seasonally dominant prey items in the spring, summer, and fall, respectively. G. mucronatus and calanoid copepods were consumed in approximate proportion to their numerical abundance in the environment, while E. attenuata, present in rather uniform densities throughout the study period, was extensively consumed only in the late summer and fall. An ontogenetic pattern of prey consumption was evident, in addition to the seasonal pattern, Comparison of G. mucronatus and E. attenuata size ranges from the field and in pipefish guts revealed that S. fuscus preyed upon the smaller size classes of each species, and that mean size of prey consumed was positively related to fish size. 9 1987 Estuahne Research Federation 330
Patterns and drivers of the demersal fish community of Chesapeake Bay
Marine Ecology Progress Series, 2013
Large-scale research on the environmental, biological, and anthropogenic drivers of fish distributions, abundances, and community structure can identify patterns and trends within systems, provide mechanistic insight into ecosystem functioning, and contribute to ecosystembased fisheries management. This study synthesized 10 yr of extensive fisheries-independent bottom trawl data (2002 to 2011) to evaluate drivers of demersal fish community structure in Chesapeake Bay, the largest estuary in the United States. Changes in community composition were assessed using constrained correspondence analysis. Also, aggregate community metrics (species richness, Simpson diversity, and catch-per-unit-effort [CPUE] of species groups) were modeled using generalized additive models. Five species (Atlantic croaker, white perch, spot, striped bass, and summer flounder) accounted for > 75% of the total trawled biomass. The demersal fish community was primarily structured by the latitudinal salinity gradient that largely differentiated anadromous fishes from coastal shelf spawning species and elasmobranchs, with low overall CPUE and richness in mesohaline waters. Low dissolved oxygen concentrations (below ~4 mg l −1) greatly suppressed CPUE and diversity metrics and appeared to displace fish biomass toward the northern and southern edges of the bay's mainstem channel. Water temperature and month strongly influenced the seasonal dynamics of community composition and metrics. Community composition and biomass shifted after 2007, with a substantial decline in annual CPUE of some species groups. Recruitment and fishing indices for the dominant species were the best predictors of the interannual patterns in community metrics, outperforming various other climatic and biological annual-scale covariates.