NOTES 



EFFECTS OF DESICCATION AND AUTOSPASV 



ON EGG HATCHING SUCCESS IN 



STONE CRAB, MEMPPF MERCES ARIA 



The stone crab. Menippe mercenaria, is found from 

 North Carolina to Yucatan, Mexico, Cuba, 

 Jamaica, and the Bahamas; commercial fishing 

 occurs principally in the State of Florida. Crabs 

 are captured in wooden or plastic traps (40  40  

 28 cm) baited with available fish scraps. Present 

 Florida laws allow harvest of both claws from all 

 crabs, including ovigerous females, provided each 

 claw is of legal size (70 mm propodus length). Sale 

 of whole crabs is prohibited, and declawed crabs 

 are relea.sed to allow regeneration of lost claws 

 and renewal of fishable stocks. Regeneration of 

 another legal claw can occur within 18 mo (Sulli- 

 van'). 



The commercial season extends from 15 October 

 to 15 May. Spawing occurs during the warmer 

 months (Noe 1967; Cheung 1969), and females 

 with large external egg masses (sponge) of up to 

 600,000 eggs are observed from early March to 

 late November. Newly extruded eggs, attached to 

 abdominal pleopods, are red-orange and progress 

 to yellow then grey over a 9-12 day maturation 

 period. Larvae generally hatch directly from eggs 

 attached to pleopods. Most commercial operations 

 maximize daily marketable claw yield by pulling 

 traps continuously and declawing crabs only dur- 

 ing the return trip to port. This necessitates keep- 

 ing whole crabs in large fish boxes or containers on 

 deck that are exposed to air for up to 8 h. Claw 

 removal from air-exposed ovigerous females and 

 desiccation of exposed egg masses may reduce lar- 

 val hatching and recruitment. Since these proce- 

 dures violate Florida law requiring crabs to be 

 declawed immediately and released in the same 

 area where captured, this study was conducted to 

 provide scientific data to implement change in 

 current fishing methods and protect future stocks. 



Mtthiids 



Gravid stone crabs were captured in the Gulf of 

 Mexico (5-9 ml west of Pass-A-Gnlle Beach, St. 



Petersburg, Fla., between March and September 

 1977. Females with large egg masses were trans- 

 ported in 4 1 containers by ship to the Florida De- 

 partment of Natural Resources Marine Research 

 Laboratory. St. Petersburg. Container water, ex- 

 changed frequently with Gulf water while sampl- 

 ing, was not changed for approximately l'/2 h dur- 

 ing transport through low salinity waters. 



Unfed crabs were kept individually in plywood 

 tanks divided into compartments (45.7 x 30.5 x 

 30.5 cm), sealed with fiber glass'tape and epoxy, 

 and leached 2-4 wk prior to use. Water in the 

 closed system was maintained at 15 cm depth by 

 removable standpipes, and overflows were di- 

 rected into individual glass tanks where eggs or 

 larvae were retained before water entered two 

 1,000 1 undergi-avel filter vaults (Dugan et al. 

 1975) (Figure 1). Overflow splash and two airlift 

 standpipes maintamed aeration. 



Hatching 

 tank 



Glass tank 



screen 



'J. R. Sullivan, Florida Department of Natural Resources. 

 Marine Research Laboratory, pers. commun. May 1977. 



FliU'UK I— Hatchint; lank i4.") 7  .30..')  :30,.5 cml and glas.s 

 larval capture tank (15 x 15 x 30 cm) for desiccation and auto- 

 spasy experiments with ovigerous stone crabs. 



FISHERY BULLETIN VOL. 



. NO :). 1980, 



695 



