ISOPODA 



Isopods never were abundant but were present in most of the plankton net 

 catches. Some were observed to be parasitic on small fish. On several occasions, 

 examination of larval and juvenile fish found dead in aquaria revealed an isopod 

 firnnly attached to the gills. This suggests that parasitic isopods may be respon- 

 sible for numerous fatalities of small fish in the lagoon and similar areas. 



AMPHIPODA 



Amphipods of the suborders Gammaridae and Caprellidae were of common 

 occurrence. They seldom were abundant and no pattern was evident. 



DECAPODA Shrimp and Crabs 



Identification of pre -juvenile forms of many of the shrinnps occurring in the 

 Gulf of Mexico is in an uncertain status. Adults of at least four fannilies occur 

 in the lagoon, namely: Penaeidae, Sergestidae, Crangonidae, and Palaemonidae. 

 Unquestionably, the very young of these shrimp also occur in the area. Due to the 

 uncertainty of identification, only those occurrences where positive identifications 

 were nnade are presented. 



Post-larval peneid shrimp were observed in great abundance on March 8 

 and August 4, 1955; May 14, 1956; and April 25, 1957. They were swimnning at 

 the surface and so concentrated that several thousand could be caught with a 

 single scoop of a dip net. On each occasion, large numbers of fish (mostly pinfish 

 and anchovies) could be seen decimating the relatively helpless shrimp. An 

 interesting observation was made during the August occurrence. The post-larval 

 peneids were concentrated in a winding "band", a foot or more in width, that ex- 

 tended from the culverts well out into Bolivar Roads. 



Adult and young white shrimp, Penaeus setifems (Linnaeus), were taken from 

 time to time by cast net in area "A", chiefly in the spring and fall. The series 

 of seven seine hauls made there in November 1955 yielded an average of 96 

 young and adults, ranging in length from 5.0-12.5 cm. 



Adult and young of the Sergestid shrimp, Lucifer faxoni Borradaile, were taken 

 in small numbers in every month during the period except in December, January, 

 and February. 



Crangonidae, or snapping shrimp, were never taken in the plankton catches 

 but were found occasionally under submerged rocks along the nnargin of the basin 

 during the warmer months. Three adults lived for nearly a year in a 30 -gallon 

 aquarium. 



Young Palaemonid shrimp appeared infrequently in the plankton collections 

 but were present in abundance along the shores of the lagoon except during 

 severe cold weather. These hardy grass shrimp thrive well in aquaria. Although 

 a large number of females with eggs were held for a long as 6 months, none 

 were ever observed to spawn. 



PORCELLANIDAE Porcelain Crabs 



Zoeae of porcelain crabs occurred occasionally in the plankton collections, 

 usually with large numbers of zoeae and/ or megalopa oi Callinectes snpidus Rathbun. 

 Except for one occasion, July 22, 1954, when over 500 specimens were present, 

 these unusual zoeae occurred as individual specimens or in very small numbers. 



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