Multispecies fish recruitment patterns within Chesapeake Bay were investigated in four fishery-independent survey data sets (one primary and three ancillary data sets) that together span the years 1968–2004. These independently conducted surveys record interannual recruitment variability for 15 ecologically and economically important fish species of the Northeast US Continental Shelf Large Marine Ecosystem. Principal component analyses revealed that the strongest multispecies recruitment pattern (first principal component) present in each data set describes a negative recruitment relationship between anadromous and coastal shelf-spawning species. Among the data sets, the first principal component accounted for 31%–42% of multispecies variance. Locally weighted regression modeling revealed that the decadal-scale variability accounted for 62% of the variance in the primary data set’s first principal component’s (annual) scores, whereas interannual variability accounted for only 38%. Despite strong differences in sampling methods, sampled habitats, and sampling locations, this pattern of antagonistic recruitment between Chesapeake Bay anadromous and shelf-spawning (CBASS) species was synchronously correlated among data sets at both decadal and interannual scales. The CBASS pattern has tended to persist in one mode for periods lasting longer than a decade and tends to reverse sign rather within only 2–3 years. A statistically significant regime shift occurred in 1992, when recruitment in anadromous fishes became favored at the expense of recruitment of shelf-spawning estuarine-dependant fishes.

Production indices for juvenile striped bass Morone saxatilis in the Chesapeake Bay and RoanokeRiver-Albemarle Sound regions have declined in recent years. A concurrent decline in harvest of striped bass along the Atlantic coast also has been observed. Lack of the occurrence of a dominant year class in the Chesapeake Bay since 1970 has affected the coastal harvest and the abundance of the spawning populations. Occurrence of another dominant year class will depend on two factors: relatively good survival between the egg and juvenile life stages; and a sufficient amount of egg deposition to take advantage of the good survival conditions.

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Abstract.-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.

Eggs of Atlantic silverside, Menidia menidia, were fertilized and incubated at 15, 17, 20, 25 and 30 C. The times to hatching at each temperature were 27.0, 12.4, 9.8, 4.8 and 3.0 days respectively. Thermal shocks of +8 C produced 0% mortality for larvae reared at 17 and 20 C, 19% for larvae reared at 25 C, and 11% for larvae reared at 30 C. Thermal shocks of q-•[4 C produced 3% mortality for larvae reared at 17 C, 0% for larvae reared at 20 C, and 100% for larvae reared at 25 and 30 C. Since the larvae of Menidia menidia are present in Long Island Sound when temperatures are in the 15-20 C range, it appears that the population will undergo a minimum of stress due to thermal shock as a result of nuclear power plant development on Long Island.