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Fishery Bulletin 89(3), 1991 



tures of 16-31°C. Paralarval seasonality in Louisiana 

 is similar to that of the eggs off Galveston; therefore, 

 in the northern Gulf of Mexico, L. brevis appears to 

 hatch year-round except for the coldest months. This 

 contrasts with the situation around the mouth of 

 Chesapeake Bay, near the northern limit of the species' 

 range, where paralarvae are found only during the 

 warmest months of late summer (Vecchione 1982a). 

 Laughlin and Livingston (1982) concluded that fluc- 

 tuations in the abundance of trawl-caught L. brevis in 

 the Apalachicola Estuary, Florida are related to zoo- 

 plankton biomass in the estuary, and they implied that 

 this relationship results from the squid feeding on 

 planktonic copepods. Juvenile and adult L. brevis ac- 

 tually feed on larger prey, mostly nektonic fishes and 

 shrimps (Hanlon et al. 1983). Therefore, I believe that 

 the correlation that Laughlin and Livingston (1982) 

 described results from covariance of squid and zoo- 

 plankton abundance with other independent factors 

 such as salinity and current patterns. However, plank- 

 tonic copepods are likely the natural prey for paralarval 

 L. brevis. Copepods in the zooplankton samples 

 reported here were abundant year-round, with spring 

 and fall abundance peaks; even during midwinter, 

 abundances >1000/m 3 were common. Although the 

 concentration of natural food required for successful 

 feeding by the paralarvae is not known, it does not 

 seem likely that food limitations are responsible for the 

 seasonal distribution found for the paralarval squids. 

 It is possible, though, that factors such as seasonal 

 storms that affect transport processes or patch dimen- 

 sions of the prey are as important as temperature in 

 controlling paralarval seasonality. 



Paralarval L. brevis were found most often near the 

 bottom in nearshore coastal waters. However, an im- 

 portant layer of the water column that was not sam- 

 pled is the surface microlayer. Paralarval Loligo pealei 

 in the Middle Atlantic Bight were far more abundant 

 in neuston samples than in samples from subsurface 

 waters, although they were larger in subsurface waters 

 (Vecchione 1981). I inferred from this pattern that 

 L. pealei hatchlings ascend to the surface for first feed- 

 ing on the concentrated zooplankton of the neuston, 

 and then shift ontogenetically to deeper waters. Para- 

 larval L. brevis were also larger in bottom waters than 

 near the surface. Neuston samples in waters of coastal 

 Virginia collected paralarval L. brevis in comparative- 

 ly large numbers (Vecchione 1982a). Thus, this species 

 may undergo a similar ontogenetic vertical migration, 

 but nighttime neuston sampling would be required to 

 test this hypothesis. 



It was somewhat surprising that paralarval L. brevis 

 were found in waters considered to be hypoxic. Recent 

 evidence (Wells et al. 1988, Vecchione In press b) 

 indicates, however, that this species is capable of ad- 



justing to low concentrations of dissolved oxygen by 

 increasing oxygen uptake rates. Although no experi- 

 mental evidence exists to show when in the life history 

 this capability develops, my distributional data suggest 

 that the paralarvae also have some means of coping 

 with hypoxia. This would be a very important adapta- 

 tion for a bottom-spawning species in coastal waters 

 of the northern Gulf of Mexico. The bottom waters of 

 this area seasonally become hypoxic during the salinity- 

 stratified conditions of midsummer (Pokryfki and Ran- 

 dall 1987, Turner et al. 1987), causing catastrophic 

 changes in the benthic fauna (Harper et al. 1981, 

 Gaston 1985) and shifts in the distribution of nekton 

 (Pavela et al. 1983). 



Feeding 



This is the first published analysis of stomach contents 

 for paralarval cephalopods. The incidence of solid food 

 material in the digestive organs may appear to be low 

 but, when compared with feeding studies on trawl- 

 caught squids, does not seem unreasonable. For in- 

 stance, Dragovich and Kelly (1963) found that among 

 1684 adult and juvenile L. brevis trawled from Tampa 

 Bay, 80% of the stomachs were empty; of those <40 

 mm in "body length," 94% had empty stomachs. 

 Similar results have been found for other species of 

 loliginids. One substantial difference between the 

 paralarval stomach contents and those of larger squids 

 is the dearth of recognizable hard parts in the ingested 

 food of the paralarvae. This makes identification of the 

 prey organisms even more difficult for paralarvae than 

 for adults and juveniles, which bite their food into 

 pieces and then swallow the pieces whole, including 

 skeletal material. However, paralarvae of another 

 loliginid, Loligo vulgaris, when feeding on small 

 shrimp, can remove and ingest the soft tissue of the 

 shrimp and discard the exoskeleton (S. v. Boletzky, 

 Laboratoire Arago, Banyuls-sur-Mer, France, pers. 

 commun., 1985). Recently, immunoassay methods have 

 been developed to allow specific identification of very 

 small samples of macerated food (e.g., Theilacker et 

 al. 1986); such methods may be required for identifica- 

 tion of gut contents in paralarval squids. 



Determination of the number of animals that had fed 

 was further complicated by the lack of differentiation 

 between the stomach and caecum in small paralarvae 

 and the frequent presence of either clear fluid or mush- 

 like fluid in the combined stomach/caecum. This fluid 

 is reminiscent of the caecal fluid in older squids that 

 are well along in digesting a meal. Alternatively, the 

 fluid may be largely seawater swallowed either natural- 

 ly or during fixation or may be spontaneously secreted 

 digestive fluids. Without knowing the dynamics of 



