Seasonal Composition of Finfish in Waters Behind the Virginia Barrier Islands

Semi-monthly sampling of finfish was conducted in the lagoons and marshes behind Parramore and Cedar Islands at Wachapreague Inlet, Cobb and Wreck Islands at Sand Shoal Inlet, and on the northwest side of Fisherman Island from September 1986 through September 1987. Although all lifestages were collected, the study was designed to focus on utilization of this area by juvenile finfish. Sixty-nine species offinfish were collected. Species diversity and abundance fluctuated widely among seasons. Both were highest in the fall and lowest in the winter. The most abundant species over all seasons and locations were silversides (Menidia menidia) and bay anchovy (Anchoa mitchilli). The most abundant commercially and recreationally important species collected were summer flounder (Paralichthys dentatus) and the sciaenids, croaker (Micropogonias undulatus ), spot (Leiostomus xanthurns) and weakfish ( Cynoscion regalis ). As adults, these species migrate inward in the spring and leave in the fall, but newly recruited juveniles were found utilizing these areas almost all year. Comparisons were made with results from the only other directed study in this area (Richards and Castagna, 1970). Differences between the results of these two studies can be attributed to gear (size of trawl net mesh) and site (salinity and relative position in marsh)

Hypothetical Northern Spawning Limit and Larval Transport of Spot

The exact northern limit of the spawning grounds of spot (Leiostomus xanthurus) has not been determined. Previous reports of spot spawning during the winter/spring in the Middle Atlantic Bight (MAB) are refuted based on the presence of low bottom-water temperatures at that time. Analyses of historic bottom isotherms in the MAB during winter/spring show that the most northerly occurrence of required 17° C bottom temperatures from December to May is on the outer continental shelf off North Carolina near the Gulf Stream. It is therefore suggested that spot recruiting to Chesapeake Bay are spawned near Cape Hatteras at the shelf break in winter. (more ...)https://scholarworks.wm.edu/vimsbooks/1145/thumbnail.jp

Interannual Variation In The Recruitment Pattern And Abundance Of Age-0 Summer Flounder, Paralichthys-Dentatus, In Virginia Estuaries

Capture of transforming larval and newly settled juvenile (age-0) summer flounder, Paralichthys dentatus, over four years (1986-1989) in the seaside salt marshes of Virginia\u27s Eastern Shore and in the lower Chesapeake Bay verifies Virginia waters as a nursery area. Gear specific for juvenile flatfish was used and sampling was conducted in a broad range of habitats in all months. This study demonstrates a fluctuation in the timing of the appearance and magnitude of abundance of age-0 summer flounder in Virginia waters over a four-year sampling period. Age-0 summer flounder (11-27 mm TL) began entering the area in October 1986 and were present throughout the winter of 1987. The 1988 and 1989 year classes did not appear until April at larger sizes (22-83 mm TL). Highest catch per unit of effort (CPUE) occurred between April and August and abundance declined in the fall. Data indicated that year-class strength declined from 1986 to 1988 and increased slightly in 1989. To monitor year-class strength of age-0 summer flounder, we recommend sampling Virginia estuaries in April, May, and June when both abundance of flounder is high and small-mesh-lined trawl gear is most efficient

Climate scale environmental factors affecting year-class fluctuations of Atlantic croaker (micropogonias undulatus) in the Chesapeake Bay (Maryland, Virginia)

A conceptual life history of the Atlantic croaker (Micropogonias undulatus) identifies the effects of the environment on juvenile recruitment. In a multi-disciplinary approach to modelling, the major effects are investigated, quantified and presented in a flow chart. The model is divided into three sub models, each representing a major component which affects juvenile recruitment. North/south spawning location in the Mid-Atlantic Bight is affected by the bottom water temperature as influenced by the cessation of the summer winds in relation to timing of croaker migration. The pelagic phase is the most critical time in the life history of a larval croaker as they are subjected to wind-induced transport which may cause direct loss off the shelf and entrainment in the Gulf Stream, or indirect loss by prolonging time in transit to the nursery area. The magnitude of this wind-included effect is a function of the direction, strength, duration and time relative to spawning and is incorporated in an equation to predict year-class strength of croaker. The juvenile croaker overwinter in the Chesapeake Bay system. Winter temperature is shown to be the predominant variable affecting year-class survival to the following summer in very cold years. However, in very warm years, the predictive capabilities of the model are improved when a measure of fall recruitment, i.e. wind-induced transport, is incorporated. Croaker is basically a density-independent stock as, juvenile recruitment is erratic and dependent upon these environmental parameters. The effect of spawning stock size is only apparent after accounting for density-independent effects, and slightly improves the explained variance of the statistical relationship. Year-class strength and fishing pressure cause interannual variability in commercial catch. Overfishing a weak year class reduce spawning potential, and several poor year classes in a row magnify this. The moel, tested for the 1982-83 data, predicts a strong year class

The VIMS Trawl Survey : Juvenile Atlantic Croaker

An index of juvenile croaker recruitment was developed to test proposed relationships between juveniles and environmental factors. The VIMS trawl survey data base is unique on the east coast because of its duration and continuity. No other data set exists that samples the same species in the same locality with concurrent physical data over a long period of time

The Barents and Chukchi Seas: Comparison of two Arctic shelf ecosystems

This paper compares and contrasts the ecosystems of the Barents and Chukchi Seas. Despite their similarity in a number of features, the Barents Sea supports a vast biomass of commercially important fish, but the Chukchi does not. Here we examine a number of aspects of these two seas to ascertain how they are similar and how they differ. We then indentify processes and mechanisms that may be responsible for their similarities and differences.Both the Barents and Chukchi Seas are high latitude, seasonally ice covered, Arctic shelf-seas. Both have strongly advective regimes, and receive water from the south. Water entering the Barents comes from the deep, ice-free and "warm" Norwegian Sea, and contains not only heat, but also a rich supply of zooplankton that supports larval fish in spring. In contrast, Bering Sea water entering the Chukchi in spring and early summer is cold. In spring, this Bering Sea water is depleted of large, lipid-rich zooplankton, thus likely resulting in a relatively low availability of zooplankton for fish. Although primary production on average is similar in the two seas, fish biomass density is an order of magnitude greater in the Barents than in the Chukchi Sea. The Barents Sea supports immense fisheries, whereas the Chukchi Sea does not. The density of cetaceans in the Barents Sea is about double that in the Chukchi Sea, as is the density of nesting seabirds, whereas, the density of pinnipeds in the Chukchi is about double that in the Barents Sea. In the Chukchi Sea, export of carbon to the benthos and benthic biomass may be greater. We hypothesize that the difference in fish abundance in the two seas is driven by differences in the heat and plankton advected into them, and the amount of primary production consumed in the upper water column. However, we suggest that the critical difference between the Chukchi and Barents Seas is the pre-cooled water entering the Chukchi Sea from the south. This cold water, and the winter mixing of the Chukchi Sea as it becomes ice covered, result in water temperatures below the physiological limits of the commercially valuable fish that thrive in the southeastern Bering Sea. If climate change warms the Barents Sea, thereby increasing the open water area via reducing ice cover, productivity at most trophic levels is likely to increase. In the Chukchi, warming should also reduce sea ice cover, permitting a longer production season. However, the shallow northern Bering and Chukchi Seas are expected to continue to be ice-covered in winter, so water there will continue to be cold in winter and spring, and is likely to continue to be a barrier to the movement of temperate fish into the Chukchi Sea. Thus, it is unlikely that large populations of boreal fish species will become established in this Arctic marginal sea. © 2012 Elsevier B.V

Some Thoughts on Estimating Change to Arctic Cod Populations from Hypothetical Oil Spills in the Eastern Alaska Beaufort Sea

We describe a fecundity-hindcast model that incorporates Arctic cod Boreogadus saida acute toxicity data, field studies of Arctic cod larval distribution and abundance, natural mortality estimates for Arctic cod eggs and larvae, and an oil spill fate model in Alaska Beaufort Sea. Three orders of magnitude of spill events (1,000 tons, 10,000 tons, 100,000 tons) were evaluated for both physically and chemically dispersed oil. Using worst-case assumptions in our model, a 100,000-ton spill of crude oil treated with dispersants resulted in 266 million m3 of water that exceeded our acute toxicity threshold, compared to a volume of 71 million m3 for a 100,000-ton spill not treated with dispersants, and resulted in exposure of about 2 million Arctic cod larvae remaining from an initial 87 million eggs. This represents the reproductive output of about 7,300 adult females. Adult Arctic cod populations in the Alaska Beaufort number in the 10s to 100s of millions. The results show that even with an order of magnitude variation in exposure, the effect of dispersing a large oil spill on the regional cod population is expected to be insignificant (~0.7%). The recent hiatus in Arctic oil and gas development affords an opportunity to acquire additional data to further strengthen this conclusion.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author