We describe a method to sample the highly contagious distribution of pelagic ®sh eggs. CUFES, the continuous, underway ®sh egg sampler, consists of a submersible pump, concentrator, electronics and sample collector. This system operates continuously and under nearly all sea conditions, providing a real-time estimate of the volumetric abundance of pelagic ®sh eggs at pump depth, usually 3 m. CUFES-derived estimates of volumetric abundance agree well with those from nets towed at pump depth and with areal abundance estimated from vertically integrated plankton tows. CUFES has been used successfully to sample the eggs of menhaden, pin®sh, sardine, and anchovy off the coasts of the eastern and western United States and South Africa. Two large patches of eggs of the Atlantic menhaden were sampled off North Carolina in winter 1993±94, had a linear scale of 5±10 km, and were found in waters between the Gulf Stream and mid-shelf front. Spawning location may be related to bathymetry. CUFES is now being used to estimate spawner biomass by the daily egg production method. An optical plankton counter provided accurate estimates of the number of Atlantic menhaden eggs sample by CUFES.

Seasonal distribution, abundance, habitat use, hatch dates, growth, and mortality of larval blueback herring Alosa aestivalis and alewife A. pseudoharengus were studied in the Roanoke River watershed, downstream from the Roanoke Rapids Dam in North Carolina. Ichthyoplankton was sampled from man-made canals, a creek, an oxbow, a flooded bottomland hardwood forest, the main river channel, and along the river's edge. To identify larval clupeids, we developed a dichotomous key for clupeids found in the study area using morphometric, meristic, and pigmentation characters synthesized from the literature. Distribution, abundance, and back-calculated hatch dates of larvae and eggs were used to describe spawning period, spawning habitat, and nursery habitat. Blueback herring and alewife eggs and larvae were present from early April through late May. Based on the presence of eggs and early-stage larvae, both species spawned in backwater tributary systems, including flooded bottomland hardwood forests. Our results indicated that blueback herring and alewives used a variety of habitats during early larval stages, though interspecific differences in concentration among habitats were evident. Blueback herring used both lotic (moving water) and lentic (still water) habitats, and alewives were more abundant in lentic habitats. Larval growth varied between years but not between species. Blueback herring growth rates were 0.60 mm/d in 1996 and 0.42 mm/d in 1997 compared with growth rates of 0.65 mm/d in 1996 and 0.41 mm/d in 1997 for alewives. Interspecific and between-year differences in daily mortality of preflexion blueback herring and alewives (age, 4-8 d) were observed. Blueback herring daily percent mortality in 1996 and 1997 was 99%, while alewife rates decreased from 98% in 1996 to 91% in 1997. Fluctuations in river flow affected habitat use; moderate to high discharge rates increased use of spawning and nursery habitats, and low flows reduced use of spawning habitat.

No abstract

Juvenile pinfish Lagodon rhomboides and spot Leiostomus xanthurus exposed to pressure waves emanating from experimental submarine detonations exhibited both sublethal and probable antemortem trauma. Hyperemia within the swim bladder and liver, hematuria, coagulative liver necrosis, and rupture of the pancreas were the most recurrent and significant traumas evident from histopathological examination and were directly attributed to exposure to pressure waves. These traumas were probably caused by the rapid compression and expansion of the swim bladder as the impulse passed. Of these traumas, hyperemia within visceral organs and hematuria are probably sublethal. Rupture of the pancreas and coagulative liver necrosis are typically irreversible and hence probably antemortem.