BROWN and CAPUTI: FACTORS AFFECTING GROWTH OF ROCK LOBSTER 



MINUTE = MINUTE EXPOSURE ETC 



2 3 U b 6 1 



NUMBER OF MISSING APPENDAGES 



Figure 3— Two Rocks, November-December 1979. The mean size increment related to exposure categories and number of missing 

 appendages for animals recaptured from February 1980 onwards. Exposure and missing appendages categories with less than five 

 individuals have been combined and are plotted at the mean appendage level. The sample sizes are shown next to the points. 



3) Size of these animals on reaching maturity would 

 also be reduced, which would cause a decrease 

 in fecundity directly proportional to their reduced 

 size (Morgan 1972). The time they would take to 

 reach maturity would probably not be affected 

 since age appears to determine maturity rather 

 than size (Chittleborough 1974d). 



4) Affected animals would remain undersize for 

 longer, thereby increasing the possibility that they 

 could undergo multiple capture and handling. 

 Multiple handling would result in increased mor- 

 tality and further reduced growth. 



These factors, when added to the estimate of 

 14.6% reduction in recapture rate (most likely due 

 to mortality) of the returned undersize lobsters dur- 

 ing the fishing season (Brown and Caputi 1983), con- 

 stitute a serious loss to the fishery. In addition, any 

 mortality and reduced growth which may occur as 

 a result of lifting the animals to the surface and 

 returning them to the sea would also need to be add- 

 ed to the above loss. This loss could not be quantified 



as both experimentals and controls in the tagging 

 experiments experienced this. 



As mentioned by Brown and Caputi (1983), use of 

 more effective escape gaps and an education pro- 

 gram to encourage fishermen to return their under- 

 size rock lobsters immediately to the sea while their 

 vessel remained in the immediate vicinity of where 

 the pot was pulled would help to overcome this 

 serious source of industry created wastage Both 

 these approaches are currently being examined wdth 

 a view to reducing the numbers of undersize lobsters 

 that are handled and the time they are kept on board 

 the vessels. 



ACKNOWLEDGMENTS 



The authors would like to thank J. Prince and J. 

 Jenke for technical assistance during this work; Ron 

 Duckrell, the skipper, and the crew of the Flinders 

 for assistance during the tagging trials; D. A. Han- 

 cock and N. Hall for critically reading the manu- 

 script and offering many helpful suggestions; and 



573 



