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Sebastes carnatus and Sebastes chrysomelas are morphologically and ecologically similar residents of rocky reefs off the coast of California. They segregate bathymetrically, with S. chrysomelas occurring shallower than S. carnatus. Each species extended its depth distribution where its congener was removed, and no distributional changes occurred in a control area. Thus both species tolerated conditions beyond their normal depth ranges, and were limited in part of their normal depth ranges by interspecific competition. Their segregation was apparently initiated by the preferential settlement of young fish from the plankton, S. chrysomelas in shallow water and S. carnatus deeper. Their segregation was maintained by interspecific territoriality. The distribution of S. chrysomelas, the socially dominant species, may also have been affected by a strong preference for food—rich areas that occurred mainly in shallow water. I postulate that such a preference would be due to the advantage of smaller home ranges in shallow water, where strong wave surge makes the shelter hole a more important part of a fish's territory. This postulated preference, along with aggression from S. carnatus, limited S. chrysomelas to shallow water. Because of its social dominance, S. chrysomelas aggressively excluded S. carnatus from preferred areas in shallow water.

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SynopsisSeasonal cycles of reserve deposition and utilization in many fishes, amphibians and reptiles alleviate temporal mismatches of energy supply and demand. Utilization of reserves can be related to maintenance during periods of reduced food supply, to reproduction, particularly during periods of poor food availability, and to migration. Published data on the seasonal cycles of reserves and reproduction in Sebastes suggest that reserves are important for maintenance during wintertime periods of low food availability. Unlike many other ectothermic vertebrates, some species of Sebastes deposit fat reserves at the same time as gametogenesis, a pattern consistent with the longevity and iteroparity evident in the genus. Other species of Sebastes have similar seasonal timing of fat cycles, but since reproduction takes place later in the year, the decline in reserves during winter coincides with the main period of reproductive activity. The significance of this is not clear. Interspecific differences in amounts of reserves may be related to geographical differences in the seasonality or abundance of food. Intraspecific variation in reserves, marked most strongly by allometry of reserves with regard to fish length, bears further study, since it may link the proces of sexual maturation and the responses of repeat spawners to variability in food supply and other environmental factors. IntroductionIn many animals some assimilated food is allocated to reserves rather than to immediate use, in what is generally seen as a means of ameliorating temporal mismatches between food supply and energy demand (Love 1970, Shul'man 1974, Derickson 1976b, King & Murphy 1985. The particular proximate function of reserves is often indicated by the timing of reserve deposition and utilization in relation to temporal changes in environmental factors and physiological demands. Knowledge of that function can contribute to an understanding of the important factors in the relationship of an organism to its environment. The deposition and use of reserves are also important in the overall allocation of energy in an organism and thus have an ultimate function in its demography and life history. In the latter regard, costs of reserve deposition, in terms of other immediate uses to which the energy could have been applied (Slobodkin 1962, Calow 1977, are balanced against the benefits of reserve utilization, and the trade-offs are evaluated in the context of the allocation of resources to current versus future reproduction (Fisher 1958).The purpose of this paper is to describe ways that knowledge of the patterns of reserve deposition and utilization can contribute to our understanding of the ecology and life history of Sebastes. To that end, I will present some background on the functions of reserves in ectothermic vertebrates, including complications in the interpretation of these 58 functions, and then discuss past and potential future work on the role of reserves in the ecology and life history of Sebastes species. Functions of reserves in ectot...

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The evacuation patterns of shrimp, crab and fish from the stomachs of black and yellow rockfish, Sebustes chrysomelas, were examined by feeding meals of known size and measuring the amount remaining after various post-prandial intervals. Linear, square-root, exponential, power exponential, logistic and Gompertz models (the latter two with unrestricted lower asymptotes, or with lower asymptotes restricted to 0% food remaining) were fitted to the wet weight, dry weight and volume of food remaining in the stomach as a function of post-prandial time. Evacuation patterns ranged from steeply concave (fish wet weight, dry weight, volume, shrimp dry weight), to linear (shrimp wet weight, crab dry weight), to highly convex with lag phases of up to 30 h (crab wet weight, crab and shrimp volume). Friability, the ease with which a food item is fragmented in the stomach, may be an important factor in determining evacuation patterns. The evacuation of a crab meal by tagged, free-ranging S. chrysomelas in the field was not significantly different from that of S. chrysomelus held in the laboratory.

Pelagic dispersal of marine organisms provides abundant opportunity for gene flow and presumably inhibits population genetic divergence. However, ephemeral, fine-scale, temporal and spatial genetic heterogeneity is frequently observed in settled propagules of marine species that otherwise exhibit broad-scale genetic homogeneity. A large variance in reproductive success is one explanation for this phenomenon. Here, genetic analyses of 16 microsatellite loci are used to examine temporal patterns of variation in young-of-year kelp rockfish (Sebastes atrovirens) recruiting to nearshore habitat in Monterey Bay, California, USA. Population structure of adults from central California is also evaluated to determine if spatial structure exists and might potentially contribute to recruitment patterns. Genetic homogeneity was found among 414 young-of-year sampled throughout the entire 1998 recruitment season. No substantial adult population structure was found among seven populations spanning 800 km of coastline that includes the Point Conception marine biogeographic boundary. Comparison of young-of-year and adult samples revealed no genetic differentiation and no measurable reduction in genetic variation of offspring, indicating little variance in reproductive success and no reduction in effective population size for this year class. Simulation analyses determined that the data set was sufficiently powerful to detect both slight population structure among adults and a small reduction in effective number of breeders contributing to this year class. The findings of high gene flow and low genetic drift have important implications for fisheries management and conservation efforts.