Growth and Production Estimates for Biomass-Dominant Fishes on a Southern California Artificial Reef
Abstract:Somatic growth and somatic and gonadal production were estimated during May–November 1989 for six species, comprising most of the standing crop biomass of the fishes on a shallow (10- to 15-m deep), 14-year-old, quarry rock reef (Torrey Pines Artificial Reef #2, TPAR), off La Jolla, California. Growth was estimated from weight-converted length increments of 142 Floy-tagged individuals at liberty for a median of 187 days. Egg production was estimated for females of three taxa (four species) as the product of the weight of batch egg production and spawning frequency (the latter determined from histological evidence of day-old postovulatory follicles). Milt production was deduced from male to female ratios of gonad weights for reproductive fish. Somatic growth rates varied three- to fourfold among the six species and, in part, reflected the distribution of maturity stages of intraspecific populations. On average, the per capita growth rates of taxa dominated by immature stages were faster than those dominated by large adults. Somatic production varied more than somatic growth rates (by a factor of 15), because of additional variations in standing stock biomass among populations. The somatic production of at least one species was underestimated as a result of a tag effect on growth. Weight-specific egg production varied only twofold among the three taxa examined, perhaps because fishes with smaller batch egg productions compensated by spawning more frequently, and vice versa. Estimates of weight-specific milt production further diverged because of the influence of relative testis-to-ovary weights that ranged from a small fraction to unity. Additional variation among taxa in total gonadal (egg plus milt) production was about one-half that of somatic production (a factor of eight). Besides representing interspecific differences in adult biomass, variations in gonadal production reflected intraspecific differences in the biomass contributions of the two sexes within the fraction of adults that were reproductively active. Despite likely substantial underestimates of gametic materials, gonadal production ranged from a large fraction to a large multiple of somatic production among the four species. Our observations suggest that the elaboration of tissue unrelated to yield is nontrivial and represents a major component of energy flow through the fishes in this reef system and perhaps others.
Document Type: Research Article
Publication date: 1994-09-01
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