COMPONENTS OF GROWTH RATE VARIATION AMONG LABORATORY CULTURED LOBSTERS (Homarus)

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Abstract
Laboratory‐reared juvenile lobsters (Homarus americanus) vary considerably in growth rate. Up to 30% of this variation appears to be heritable, but culture system, family by system interaction, and density differences within and between systems also contribute substantial growth rate variance. Results from split‐plot analyses of growth variance among 8 families of full‐sib juveniles grown for 90 days on live, adult brine shrimp at 3 temperatures (14°C ambient, 18°C, and 21°C; 2 replications) are in complete agreement with previous findings. Family, and by implication genotype, is a significant component of growth rate variance. Environment, however, plays an even more significant role. Density of lobsters in a system at the time of stocking new families affects growth of the younger juveniles adversely. Temperature produces expected fixed effects on growth rate with no evidence of statistical interaction between family and temperature. Replication over similar, but independent, experimental grow‐out systems reveals added growth variance apparently due to uncontrolled culture system variables. Significant culture system x genotype interactions are also observed.Maternal influences and environmental effects arising from separate rearing of families until stage IV are confounded in the family differences observed in our growth studies. Two preliminary observations bearing on this problem show no evidence for a strong influence of larval history on juvenile growth.Implications from this study are (1) that selective breeding for faster growth of lobsters would probably be successful although genotype x environment interactions might make the breeding program more complex and costly; (2) that important, possibly density‐dependent, environmental factors have not been identified or controlled in studies of lobster growth; and therefore (3) that much more research is needed to verify the biological validity of current concepts of high density, commercial Lobster aquaculture.

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