Estimating Relative Juvenile Abundance of Ecologically Important Finfish and Invertebrates in the Virginia Portion of Chesapeake Bay (Project No. NA03NMF4570378) July 2004–June 2005

The fisheries trawl survey conducted by the Virginia Institute of Marine Science (VIMS) is the oldest continuing monitoring program (50 years) for marine and estuarine fishes in the United States. This survey provides a monthly baseline assessment of abundance of juvenile marine and estuarine fishes and invertebrates in the tidal and mainstem Chesapeake Bay. The survey provides crucial, real time data to various 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). For example, the VIMS Trawl Survey provides the ASMFC with the only spot index available on the East Coast and was the cornerstone for the 2003 ASMFC Spot FMP. The MAFMC recognizes the VIMS Trawl Survey as the only available predictor of summer flounder recruitment.In the Virginia portion of Chesapeake Bay, several annual indices of juvenile abundance have been generated from trawl survey data for species of key ecological, commercial and recreational importance. These include spot, Atlantic croaker, weakfish, summer flounder, black sea bass, scup, striped bass, white perch, catfishes (white, channel and blue), northern puffer, silver perch, blue crab, American eel and bay anchovy.Four different estimates of relative abundance have been developed for juvenile finfish. The Bay and River index (BRI) is only for the historic fixed station transects of the tributaries and the Bay survey established in 1988. Two indices are presented, one from the tributaries only (RO; 1979 to present) and the other for both the Bay and rivers (BRI;1988 to present). Both converted indices (random stratified converted index - RSCI) and unconverted indices (random stratified index - RSI) for the target species discussed have been created for the half century time series.In recent years, juvenile indices for most species have declined, most often a result of overfishing, degradation of their estuarine nursery habitats, and year class failure due to natural environmental variation. For example, spot RSCI indices have declined greatly over the past 50years, with their 1955-1978 indextwice the 1979-2004index.Croaker show the greatest interannual variability of the key species discussed, with fluctuations weather related. There was an increasing trend in weakfish converted indices since 1994, while summer flounder have remained low, most probably due to overfishing and year class failure, which were revealed in the very low 1987 trawl index. The black sea bass index had increased since 1997, but decreasedin 2002 and 2003 to the lowest level in decades. The scup index has been highly variable and decreased in 2003. Striped bass indices were very low during the 1970\u27s and early 1980\u27s, rebounded in the early 1990\u27s and have decreased and remained low since 2001. White perch YOY and age 1+ indices decreased in 2005 from the previous year. White catfish YOY and age 1+ indices decreased from 2004, as did the channel catfish YOY index, while the channel catfish age 1+ index increased slightly in 2004. Blue catfish indices have increased since 2001. Since 1988, northern puffer indices experienced a rapid and continuous decline. The silver perch index has remained consistently low since 1972. Both age 1+ and adult female blue crab indices exhibited significant declines. Both American eel and bay anchovy indices have decreased since the early 1980’s. The Chesapeake Bay is a major nursery area for many coastal migratory fish species and an integral part of multistatemanagement efforts along the Atlantic Coast of the United States. 10INTRODUCTIONA key element in the management of the Atlantic States\u27 coastal fishery resources is the use of juvenile abundance estimates (indices) of important finfish and invertebrates. Relative interannual abundance estimates of early juvenile (age 0) fish and crustaceans (i.e.,blue crab, Callinectes sapidus) generated from scientific (fishery-independent) survey programs provide a reliable and early estimator of future year class strength (Goodyear, 1985; Lipcius and Van Engel, 1990), and may be used to validate management actions. The Chesapeake Bay Stock Assessment Committee (CBSAC), a federal/state committee sponsored and funded by the National Oceanic and Atmospheric Administration (NOAA) reviewed previously available indices of juvenile abundance for important fishery resource species in the Chesapeake Bay (hereafter referred to as “Bay”) and recommended that a unified, consistent trawl program should be one of the primary monitoring tools for finfish and crab stock assessment (Chesapeake Bay Program Stock Assessment Plan, Chesapeake Executive Council, 1988). Subsequently, CBSAC supported pilot studies directed at developing a comprehensive trawl survey for Chesapeake Bay. The primary focus of this support in the Virginia portion of the Bay was the initiation (1988) of a monthly trawl survey of the mainstem lower Bay. This effort complimented and expanded the monthly trawl surveys of the major Virginia tributaries (James, York and Rappahannock Rivers), which had been conducted by the Virginia Institute of Marine Science (VIMS) as part of a long-term monitoring effort to assess the condition of fishery stocks in the lower Chesapeake Bay and its tributaries. The present sampling program, which includes the Bay and its tributaries, is vital in insuring that data are of sufficient geographic resolution for the generation of annual relative estimates of recruitment success of ecologically, commercially and recreationally important 11finfish and crustacean species. The National Marine Fisheries Service (NMFS) Marine Recreational Fisheries Statistics Survey (MRFSS) 2004 survey for Virginia marine recreational catches were dominated by Atlantic croaker (Micropogonias undulatus), summer flounderflounder (Paralichthys dentatus), spot (Leiostomus xanthurus), striped bass (Morone saxatilis),black sea bass (Centropristis striata), bluefish (Pomatomus saltatrix), pigfish (Orthopristis chrysoptera), weakfish (Cynoscion regalis), and kingfishes (Menticirrhus spp.; Anon., 2004; see Table 1). These are the top species landed by catch (89% of the total catch) and weight (84% of the total weight; Table 1). These species depend upon the lower Chesapeake Bay and its tributaries as a nursery area, with all but bluefish highly vulnerable to bottom trawls. In addition to the key species above, past survey results indicate other species of recreational interest, including scup (Stenotomus chrysops), white perch (Morone americana), silver perch(Bairdiella chrysoura), and freshwater catfishes (white, Ictalurus catus, channel, I. punctatus,and blue, Ictalurus furcatus), are taken with sufficient regularity during trawling operations to provide datasets suitable for the generation of juvenile abundance indices. Although generation of annual juvenile (young-of-year or YOY) indices is the primary focus of this project, survey results can be used to address other aspects of finfish population biology, such as habitat utilization, early growth and survival, climate and pollutant interactions, or disease prevalence. For example, climate effects such as hurricanes affect recruitment of shelf spawning species such as Atlantic croaker (Montane and Austin, 2005). Additionally, a high level of hurricane activity is predicted for the Chesapeake Bay for the next 10-40 years (Goldenberg et al., 2001), likely impacting different species abundance and distribution, and consequently multispecies interactions