768 research outputs found

    High salinity tolerance of invasive blue catfish suggests potential for further range expansion in the Chesapeake Bay region

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    In estuaries, salinity is believed to limit the colonization of brackish water habitats by freshwater species. Blue catfish Ictalurus furcatus, recognized as a freshwater species, is an invasive species in tidal rivers of the Chesapeake Bay. Salinity tolerance of this species, though likely to determine its potential range expansion and dispersal in estuarine habitats, is not well-known. To address this issue, we subjected blue catfish to a short-term salinity tolerance experiment and found that this species tolerates salinities higher than most freshwater fishes and that larger blue catfish tolerate elevated salinities for longer periods compared with smaller individuals. Our results are supported by spatially extensive, long-term fisheries surveys in the Chesapeake Bay region, which revealed a gradual (1975–2017) down-estuary range expansion of blue catfish from tidal freshwater areas to habitats exceeding 10 psu [practical salinity units] and that large blue catfish (\u3e 200 mm fork length) occur in salinities greater than 10 psu in Chesapeake Bay tributaries. Habitat suitability predictions based on our laboratory results indicate that blue catfish can use brackish habitats to colonize new river systems, particularly during wet months when salinity decreases throughout the tidal rivers of the Chesapeake Bay

    Estimating Relative Abundance of Young of Year American Eel, Anguilla rostrata, in the Virginia Tributaries of Chesapeake Bay (Spring 2008)

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    The Atlantic States Marine Fisheries Commission (ASMFC) adopted the Interstate Fishery Management Plan (FMP) for the American eel in November 1999. The FMP focuses on increasing coastal states’ efforts to collect American eel data through both fishery-dependent and fishery-independent studies. Consequently, member jurisdictions agreed to implement an annual survey for young-of-year (YOY) American eels. The survey is intended to “
characterize trends in annual recruitment of the YOY eels over time [to produce a] qualitative appraisal of the annual recruitment of American eel to the U.S. Atlantic Coast” (ASMFC 2000). The development of these surveys began in 2000 with full implementation by 2001. Survey results should provide necessary data on coastal recruitment success and further understanding of American eel population dynamics. A recent American eel stock assessment report (ASMFC 2006) emphasized the importance of the coast-wide survey as an index of sustained 4 recruitment over the historical coastal range and an early warning of potential range contraction of the species. In 2008, the Virginia Institute of Marine Science continued its spring sampling to estimate relative abundance of YOY American eels in Virginia tributaries of Chesapeake Bay

    Evaluating Recruitment of American Eel, Anguilla rostrata, in the Potomac River (Spring 2018)

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    American Eel (Anguilla rostrata) is a valuable commercial species along the Atlantic coast of North America from New Brunswick to Florida. Landings from Chesapeake Bay typically represent 60% of the annual United States commercial harvest (ASMFC 2012). American Eel is also important to the recreational fishery as it is often used live as bait for Striped Bass (Morone saxatilis) and Cobia (Rachycentron canadum). In 2016, Chesapeake Bay commercial landings of American Eel (728,717 lbs) were 78% of the U.S. landings (personal communication from the National Marine Fisheries Service, Fisheries Statistics Division). Since the 1980s, harvest along the U.S. Atlantic Coast has declined, with similar patterns occurring in the Canadian Maritime Provinces (Meister and Flagg 1997). The American Eel Benchmark Stock Assessment report (ASMFC 2012) established that the American Eel is depleted in U.S. waters; the 2017 stock assessment update (ASMFC 2017) confirmed that this population remains depleted. Hypotheses for the decline in abundance of American Eel in recent years include locational shifts in the Gulf Stream, pollution, overfishing, parasites, and barriers to fish passage (Castonguay et al. 1994; Haro et al. 2000). The decline in abundance may or may not exhibit spatial synchrony (Richkus and Whalen 1999; Sullivan et al. 2006); additionally, factors such as unfavorable wind‐driven currents may affect glass eel recruitment on the continental shelf and may have a greater impact than fishing mortality or continental climate change (Knights 2003). Limited knowledge about fundamental biological characteristics of juvenile American Eel has complicated interpretation of juvenile abundance trends (Sullivan et al. 2006). The Atlantic States Marine Fisheries Commission (ASMFC) adopted the Interstate Fishery Management Plan (FMP) for the American Eel in November 1999. The FMP focuses on increasing coastal states’ efforts to collect American Eel data through both fishery‐dependent and fishery‐independent studies. Consequently, member jurisdictions agreed to implement an annual survey for young‐of‐year (YOY) American Eels. The survey is intended to “
characterize trends in annual recruitment of the YOY eels over time [to produce a] qualitative appraisal of the annual recruitment of 3 American Eel to the U.S. Atlantic Coast” (ASMFC 2000). The development of these surveys began in 2000 with full implementation by 2001. Survey results should provide necessary data on coastal recruitment success and further understanding of American Eel population dynamics. The recent American Eel Benchmark Stock Assessment report (ASMFC 2012) emphasized the importance of the coast‐wide survey for providing data useful in calculating an index of recruitment over the historical coastal range and for serving as an early warning of potential range contraction of the species. Funding for the Virginia Institute of Marine Science’s spring survey in the Potomac River was provided by the Potomac River Fisheries Commission, thereby ensuring compliance with the 1999 ASMFC Interstate Fishery Management Plan for American Eels

    Evaluating Recruitment of American Eel, Anguilla rostrata, in the Potomac River (Spring 2012)

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    The Atlantic States Marine Fisheries Commission (ASMFC) adopted the Interstate Fishery Management Plan (FMP) for the American eel in November 1999. The FMP focuses on increasing coastal states’ efforts to collect American eel data through both fishery-dependent and fishery-independent studies. Consequently, member jurisdictions agreed to implement an annual survey for young-of-year (YOY) American eels. The survey is intended to “
characterize trends in annual recruitment of the YOY eels over time [to produce a] qualitative appraisal of the annual recruitment of American eel to the U.S. Atlantic Coast” (ASMFC 2000). The development of these surveys began in 2000 with full implementation by 2001. Survey results should provide necessary data on 4 coastal recruitment success and further understanding of American eel population dynamics. A recent American eel stock assessment report (ASMFC 2009) emphasized the importance of the coast-wide survey for providing data useful in calculating an index of recruitment over the historical coastal range and for serving as an early warning of potential range contraction of the species. Funding for the Virginia Institute of Marine Science’s spring survey in the Potomac River was provided by the Potomac River Fisheries Commission, thereby ensuring compliance with the 1999 ASMFC Interstate Fishery Management Plan for American Eels

    Temporal dynamics of condition for estuarine fishes in their nursery habitats

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    The condition of individuals in a year class may contribute to recruitment variability due to differential survival of poor-and well-conditioned fish, but the temporal dynamics of juvenile fish condition are poorly understood. We examined inter- and intra-annual dynamics of condition for juveniles of 3 species collected from estuarine nursery areas of Chesapeake Bay from November 2010 to June 2014. We describe temporal patterns in length-based indices, the hepatosomatic index (HSI), and relative subdermal lipid estimates for juvenile summer flounder Paralichthys dentatus (n = 1771), Atlantic croaker Micropogonias undulatus (n = 3911), and striped bass Morone saxatilis (n = 874). Multiple indices provided a more complete understanding of energy-storage strategies for juveniles because temporal patterns among condition indices were not congruent for a given species. Most juvenile summer flounder and Atlantic croaker migrate from Chesapeake Bay in the fall, both species exhibited increases in subdermal lipids in the time period prior to migration. For all species, individuals that remained in the estuary during winter exhibited high HSI values, indicating a common energy-storage strategy during winter. Mean condition of juveniles varied among year classes, but differences were inconsistent among indices, suggesting that energy was differentially stored among tissues for these year classes. Densitydependent effects contributed to variation in mean condition for summer flounder and striped bass. Our understanding of recruitment variability may be improved by assessing annual differences in mean condition as revealed by multiple indic
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