FISHERY BULLETIN: VOL. 83, NO. 4 



(number of legs and antennae missing), and displace- 

 ment of undersize lobsters, resulted in a drop in 

 recapture (mainly due to mortality) of 14.6%. After 

 allowing for the natural mortality expected before 

 the undersize lobsters would reach legal size, the ef- 

 fective reduction that could be expected was 11.4%. 

 For the 1982-83 season, the loss to the fishery could 

 have been in the vicinity of $A8 million. 



An aspect of undersize lobster mortality and loss 

 of commercial production that was not discussed by 

 Brown and Caputi (1983) concerns the effect of 

 handling on the growth of these animals. If the 

 growth rate of the undersize lobster is reduced by 

 exposure, damage, and displacement, then it could 

 affect the rock lobster stock and the commercial 

 fishery in a number of important ways as discussed 

 by Davis (1981): 1) The time taken for undersize 

 lobsters to reach legal size would be increased; 2) 

 these animals would enter the commercial fishery 

 at a smaller size than those with unhindered growth; 

 and 3) the size at which these animals would attain 

 maturity would be reduced. 



Other researchers have shown that the growth rate 

 of crustaceans generally and rock lobsters in par- 

 ticular is affected by a variety of environmental 

 factors such as food availability, temperature, photo- 

 period, molt phase, injuries, shelter availability, 

 salinity, and others (Chittleborough 1974a, 1975, 

 1976; Aiken 1980). Far less information is available 

 on the effects of commercial and recreational fishing 

 practice on the growth rates of exploited rock lobster 

 or other crustacean populations (Davis and Dodrill 

 1980; Davis 1981). Information that is available deals 

 almost exclusively with the injury (damage) compo- 

 nent of fishing activities or experimentation. Injury, 

 recorded as the loss of appendages, has been shown 

 to affect significantly the growth of rock lobsters P. 

 cygnus (Chittleborough 1975) and P. argus (Davis 

 1981) and the shore crabs Hemigrapsus oregonen- 

 sis and Pachygrapsus crassipes (Kuris and Mager 

 1975). 



This paper reports effects of three major com- 

 ponents of the capture and release experience (i.e, 

 damage, exposure, and displacement) on the growth 

 rate of undersize lobsters caught from commercial- 

 ly fished populations of P. cygnus. The effect of the 

 various components was examined by tagging 

 lobsters that were exposed for various periods and 

 were displaced at different distances from their place 

 of capture, with any damage being recorded. Growth 

 of experimental animals between release and subse- 

 quent recapture was compared with that of control 

 lobsters which had not been exposed, damaged, or 

 displaced. Laboratory experiments were also con- 



ducted in which undersize lobsters were exposed for 

 various periods and their growth rates subsequent- 

 ly monitored over the next two molts. 



Consequences to the industry of any reduction in 

 growth rate are discussed in the light of results from 

 this research and the findings reported by Brown 

 and Caputi (1983). 



LABORATORY EXPERIMENTS 



Materials and Methods 



Exposed undersize lobsters were maintained 

 under otherwise near optimal growing conditions of 

 excess food, adequate shelter, and protection from 

 potential predators (see also Chittleborough 1975) 

 and their molt increment and intermolt period com- 

 pared with those of unexposed animals. 



Undersize lobsters (72-75 mm carapace length) 

 were collected from the field and transported in 

 aerated seawater tanks to the laboratory in January 

 1978. Each animal was examined for size, sex, and 

 damage. Sixty undersize lobsters with no damage 

 or maximum of one appendage missing were 

 selected and marked with numbered squares of 

 Dymo Scotch Ikpe,^ fixed to the dorsal side of the 

 carapace with Repco Super Glue and placed in open 

 circulation seawater tanks. Aquaria were checked 

 daily for molts, and animals were fed to excess on 

 whole live mussels and fresh fish. If molting had 

 occurred, the exuvia was removed and the newly 

 molted animal left for a week to harden before 

 measuring and renumbering. In January 1979, each 

 animal was allowed to undergo a minimum of two 

 molts before the entire group (Group I, consisting 

 of 4 subgroups of 15 animals) was given exposures 

 of 0, 15, 30, or 60 min at a temperature of 34°-35°C. 

 Animals that died prior to exposure were not 

 replaced. 



After exposure, undersize lobsters were returned 

 to their tanks and were checked daily for any molts 

 or deaths. Feeding and renumbering was continued 

 as for pre-exposure Every animal that survived was 

 allowed at least two molts before the experiment was 

 terminated. 



A second group of undersize lobsters (Group II, 

 consisting of 5 groups of 12 animals), collected in 

 June 1978, were treated in the exact manner as 

 described for Group I with the exception that ex- 

 posures of 0, 15, 30, 60, or 120 min at 20°-21°C took 

 place 18 mo later, in December 1979. 



^Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



568 



