1,248 research outputs found

    Sublethal effects of salinity and temperature on non-native blue catfish: Implications for establishment in Atlantic slope drainages

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    The distribution and further range expansion of non-native blue catfish Ictalurus furcatus in coastal waters throughout the United States Atlantic slope depend, in part, on the salinity tolerance of the fish. However, temperature-mediated sublethal effects of increased salinities on blue catfish biology are not yet known. We assessed the effects of salinity and temperature on growth, body condition, body composition and food consumption of juvenile blue catfish in a controlled laboratory experiment. Temperature and salinity had an interactive effect on blue catfish biology, although most fish survived 112 days in salinities up to 10 psu. At salinities 9 psu) likely will not support the full lifecycle of blue catfish, but the fish may use salinities up to 10 psu for foraging, dispersal and even growth. Many oligohaline and mesohaline habitats in U.S. Atlantic slope drainages may thus be vulnerable to establishment of invasive blue catfish, particularly given the increasing temperatures as a result of climate warmin

    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

    Reproductive Characteristics Differ in Two Invasive Populations of Blue Catfish

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    The management of invasive Blue CatfishIctalurus furcatusin Chesapeake Bay tributaries is hindered by the lackof information on its reproductive biology, which is a key component of population models used to forecast abun-dance. We quantified and compared the reproductive traits of female Blue Catfish from two populations from the tidalreaches of the James and York River subestuaries during 2015–2017. In these systems, Blue Catfish matured betweenthe ages of 6 and 10 years and spawned between May and July, with largerfish spawning earlier in the season. Dur-ing spawning events, Blue Catfish produced 2,613–68,356 eggs, with larger and olderfish producing more eggs. Fishin the more densely populated James River matured at a marginally older age but a significantly smaller size thanfishin the York River, but James Riverfish allocated more energy to reproduction. Fish in the James River also hadgreater mean values of the gonadosomatic index, relative fecundity, egg organic content, and proportion of organiccontent in the eggs. Relative fecundity of Blue Catfish decreased withfish size, contrary to observations in most otherfishes. Based on the observed variability in reproductive traits and the size dependence of relative fecundity, we recom-mend incorporation of population-specific reproductive rates into stock assessment models for invasive Blue Catfish

    2020 Annual Report Estimating Relative Juvenile Abundance of Ecologically Important Finfish in the Virginia Portion of Chesapeake Bay (1 July 2019 – 30 June 2020)

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    The Trawl Survey provides crucial data to state, regional, and national fisheries management agencies, including the Virginia Marine Resources Commission (VMRC), the Atlantic States Marine Fisheries Commission (ASMFC), the Mid‐Atlantic Fisheries Management Council (MAFMC), and the National Marine Fisheries Service (NMFS). The MAFMC recognizes the juvenile trawl survey as one of the key predictors of Summer Flounder recruitment. Annual indices of juvenile abundance have been generated from trawl survey data for species of key recreational and ecological importance in the Virginia portion of Chesapeake Bay. These include Spot, Atlantic Croaker, Weakfish, Summer Flounder, Black Sea Bass, Scup, Striped Bass, White Perch, White Catfish, Channel Catfish, Blue Catfish, Silver Perch, American Eel, and Bay Anchovy. In March 2020 the Governor of Virginia issued a stay‐at‐home order due to the COVID‐19 pandemic. As a result, we did not sample during April or May. We were able to resume sampling in June 2020 at a reduced capacity and we visited 61 sites (York River and the Chesapeake Bay). Logistical constraints resulting from policies enacted to reduce potential exposure of staff prevented us from completing the full survey. We report results from June 2020 as Appendix Table 3 as these data are not spatially consistent with previous months. We completed 897 tows from July 2019 to March 2020 and collected 318,954 fishes. Bay Anchovy continue to be the most abundant species observed in the survey, accounting for 57% of all fishes collected. Of the target species for which we provide indices of relative abundance, 12 species categories (considering YOY and age 1+ as distinct categories) exhibited below‐average abundance in 2019 – 2020 (American Eel [all three rivers], Blue Catfish YOY [all three rivers], Channel Catfish juveniles and age 1+ [all three rivers], Silver Perch YOY, Spot YOY, Striped Bass YOY, Summer Flounder YOY, Weakfish YOY, White Catfish juveniles and age 1+ [all three rivers], and White Perch YOY (James River). Five species categories exhibited average abundances Bay Anchovy, Black Sea Bass YOY, Scup YOY, White Perch YOY (York and Rappahannock rivers), and White Perch age 1+ (all three rivers). Only age 1+ Blue Catfish exhibited above‐average abundances in 2019‐2020 (all three rivers). The highest index of abundance for Blue Catfish age 1+ in the James River follows the record year of YOY Blue Catfish recruitment that occurred last year

    Evaluating recruitment of American eel, Anguilla rostrata, in the Potomac River (Spring 2021)

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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 2020, Chesapeake Bay commercial landings of American Eel (218,005 lbs) were 80% 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

    2021 Annual Report Estimating Relative Juvenile Abundance of Ecologically Important Finfish in the Virginia Portion of Chesapeake Bay (1 July 2020 – 30 June 2021)

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    The Trawl Survey provides crucial data to state, regional, and national fisheries management agencies, including the Virginia Marine Resources Commission (VMRC), the Atlantic States Marine Fisheries Commission (ASMFC), the Mid‐Atlantic Fisheries Management Council (MAFMC), and the National Marine Fisheries Service (NMFS). The MAFMC recognizes the juvenile trawl survey as one of the key predictors of Summer Flounder recruitment. Annual indices of juvenile abundance have been generated from trawl survey data for species of key recreational and ecological importance in the Virginia portion of Chesapeake Bay. These include Spot, Atlantic Croaker, Weakfish, Summer Flounder, Black Sea Bass, Scup, Striped Bass, White Perch, White Catfish, Channel Catfish, Blue Catfish, Silver Perch, American Eel, and Bay Anchovy. We completed most targeted tows this past year and only missed the upper‐river stations in the James and Rappahannock rivers and a few shallow Bay stations during July and August 2020 due to COVID‐19 safety restrictions. As a result, we could not calculate an index for American Eel in the James and Rappahannock rivers. We are also unable to calculate an index for the 2019 year‐class of Black Sea Bass due to the stay‐at‐home order that included May 2020, which was an important index month for this species. A summary of other species affected by COVID‐19 restrictions is shown in the table below. (...

    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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