PROGRESS AND PROBLEMS IN LOBSTER BROODSTOCK DEVELOPMENT

Abstract

AbstractA major impediment to commercial farming of the lobster Homarus is lack of control over reproduction. Without it, a steady supply of seed cannot be insured, nor can selective breeding be applied. The major block in the reproduction of either laboratory‐mated or wild‐caught inseminated females has been low frequency of egg extrusion. Prior to 1976, 5 extrusions were documented at the Bodega Marine Laboratory. Only one of these hatched successfully. Since late 1976, however, 10 females mated in the laboratory and 8 females inseminated in nature have successfully extruded. Of these ovigerous females, 5 hatched viable progenies and the remainder subsequently lost their eggs.Most of these reproductive events occurred during a 22‐week experiment in which laboratory‐mated and field‐inseminated females were held in large tanks (37 cm × 74 cm × 49 cm deep) in a 3 temperature × 2 photoperiod design. Mortality was highest (5/18 or 28%) in the highest temperature schedule (18–22°C), lower (3/36 or 8%) in the middle temperature schedule (14–18°C) and zero (0/18) at lower temperatures (10–15°C). Molting followed a similar ordering, 67% at high temperatures, 64% at medium temperatures and 50% at low temperatures. The rate of extrusion showed an inverse pattern with only 6% in the high, 14% in the medium and 22% in the low temperature schedules. Photoperiod had an apparent effect only in the low temperature schedule with 2 molts in the short day and 7 in the long day cycle. Ovarian maturation was monitored during the experiment by a candling technique. Candling scores are correlated with actual ovary appearance and weight for 35 females sacrificed at the study's conclusion.Progress in broodstock development has come chiefly through better husbandry (larger tanks, varied diet, as well as improved sampling techniques and record keeping practices), and in part through the success of H. gammarus females in crosses to H. americanus males. Two overall results of significance to lobster broodstock development are the evidence of shorter than 2‐year cycles in some females, and the lack of marked seasonality in reproductive activity. Two problems, in addition to understanding the complex interplay of molting and ovarian development, are shell disease and loss of eggs following extrusion.