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Environmental Biology of Fishes 30: S13, 1991. 0 1991 KIuwer Academic Publishers. Printed in the Netherlands. 9 Introduction to the symposium on rockfishes George W. Boehlert’ & Juro Yamada2 Southwest Fisheries Center Honolulu Laboratory, National Marine Fisheries Service, NOAA, 2570 Dole St., Honolulu, HI 96822-2396, U.S.A. and Joint Institute for Marine and Atmospheric Research, University of Hawaii, 1000 Pope Road, Honolulu, HI 96822, U.S.A.; Laboratory of Physiology and Ecology, Faculty of Fisheries, Hokkaido University, Hakodate, Hokkaido 041, Japan The genus Sebastes is derived from a predomin- emphaeus (Moulton 1975), to large, long-lived, antly tropical family, yet represents an important very abundant, shoaling fishes such as S. marinus, component of shelf and slope fish faunas of temper- S. alutus and S. entomelas. These latter species are ate and subarctic regions. Although ecologically commercially exploited, but fisheries for Sebastes important in many habitats, most Sebastes spp. have not typically been success stories: worldwide have reproductive and early life history features catch declined from 768,481 metric tons (t) in 1976 that are rather poorly understood. Understanding to 483,733 t in 1986 (FA0 1977,1988). During this the dynamics of the reproductive process and the time interval, the U.S. catch decreased from 17,144 ecology of early life history stages is essential to to 10,325 t and the Japanese catch decreased from knowledge of fisheries exploitation, stock dynam- 54,310 to 2006 t. A dramatic case in stock decline is ics and aquaculture. Recent research on the genus that of the Pacific ocean perch, S. alutus, for which has modified our thinking about reproduction, par- biomass estimates of the west coast stock decreased ticularly related to energetics and mechanisms in- from 144,000to 13,500 tfrom 1958 to 1975 (It0 et al. volved in the live-bearing mode of reproduction. 1987). The decline of catch in the northeast Pacific Equally significant advances have been made in is now well documented (Bracken 1987), as are our understanding of the early life history of many declines in biomass of northwest Atlantic species. species. The alarming reduction in the Japanese catch, This publication is the result of a seminar entitled combined with increased interest in coastal fisher- ‘Rockfishes of the genus Sebastes: their reproduc- ies after the establishment of 200 mi exclusive eco- tion and early life history’ convened to bring to- nomic zones in the mid-l970s, prompted aquacul- gether scientists interested in these topics and to ture research on Sebastes with the goal of releasing share the different scientific approaches taken in hatchery-raised juveniles to enhance depleted North America and Japan. In this introduction, we stocks in coastal waters (Sakai et al. 1985). In the make some brief comments on the genus and de- United States and Canada, by contrast, manage- scribe the development of the different research ment measures, often including closure of fisher- approaches. ies, have been instituted (Gunderson 1984). There The ecological importance of Sebastes is evident are clearly concerns by U.S. and Japanese scien- from its speciose nature. With a center of distribu- tists, among others, about the status of Sebastes tion in the North Pacific, this genus has the greatest stocks. diversity on the west coast of North America Diversity in reproductive biology characterizes (about 69 species), followed by the waters of Japan the family Scorpaenidae, which has some 60 genera and south to Taiwan (about 32 species), the North and 330 species in 8 subfamilies. Many of the sub- Atlantic (some 4 species), and in the Southern families are distributed in tropical and subtropical Hemisphere (at least 1species). Species range from regions from deep to shallow waters. Seven of the small, short-lived shallow-water fishes, such as S. subfamilies are characterized by a strictly ovipa- 10 rous reproductive mode, with external fertilization An intimate knowledge of the reproductive pro- and,development of eggs. In the Sebastinae, how- cess is required for aquaculture of any species, both ever, internal fertilization seems to be the rule. for brood stock management and rearing of larvae. This subfamily has been reviewed by Barsukov Similarly, knowledge of early life history and ecol- (1981), and his system of phylogeny, although dis- ogy is important, especially when juveniles are re- puted by many taxonomists, clearly demonstrates leased to the wild, as in stock enhancement. Lack the complexity of the subfamily. Four genera are of such knowledge may have impeded early at- typically recognized, with 2 species of the most tempts at enhancement of cod stocks in the United primitive (and poorly known) Hozukius, 13 of He- States and Europe (Shelbourne 1964). High densi- licolenus, 3 of Sebastiscus, and approximately 103 ties, for example, can lead to increased aggression of Sebastes. Sebastiscus has been called a subgenus in territorial species of Sebastes (Hoelzer 1987). of Sebastes by Barsukov & Chen (1978), but most Combined knowledge of reproduction and early continue to recognize it as a genus. Sebastes seems life history can increase capabilities in the areas of to be the most highly derived genus in the subfam- both fisheries and aquaculture. ily, if not in the family, from both evolutionary and Studies on reproductive biology and early life reproductive standpoints. history of Sebastes have been conducted for many The reproductive mode in Sebastes has in the years in both the United States and Japan, but the past been characterized as unspecialized lecitho- motivations for the studies differed somewhat and trophic viviparity (ovoviviparity). After mating thus led to different approaches. For both coun- and copulation, fertilization occurs within the ova- tries, the importance of Sebastes in marine fisheries ry; embryos are brooded for approximately l served a major role in stimulating research. The month, and birth (also referred to herein as either secondary motivations, however, relate to aqua- spawning or parturition) occurs with the release of culture potential in Japan and basic ecology perti- relatively undeveloped embryos or larvae, 3-9 mm nent to fisheries management in the United States. long. The contrast with matrotrophic viviparity, The two countries also have different approaches wherein the embryos receive additional nutrition to coastal marine fisheries resources; Japan has during gestation, has been questioned by recent developed an energetic aquaculture industry to re- research (Shimizu & Yamada 1980, Boehlert & plenish coastal resources while the United States Yoklavich 1984, Boehlert et al. 1986). Nutritional has concentrated on natural production and man- relationships of embryos are of great evolutionary agement of stocks. An examination of pertinent significance and have an important bearing upon publications demonstrates the differences between our understanding of reproduction in fishes. There research approaches in Japan and North America are further implications, moreover, for questions (the United States and Canada). Research papers of fishery management (Garrod & Horwood 1984), on Sebastes in North America have been dom- because reproductive energy costs in this genus inated by the topics of biology, systematics, fisher- may be higher than previously thought. ies and ecology and, to a lesser extent reproduc- Variability in reproduction may lead to implica- tion, physiology and food science (Fig. la). Japa- tions for survival at the early life history stages as nese publications, on the other hand, have been well. Sebastes flavidus appears to deposit less lipid dominated by reproduction, physiology, biology, energy reserves in El Nifio years (Lenarz & Eche- systematics and, to a lesser extent, aquaculture, verria 1986); this could conceivably lead to either ecology and fisheries. In North America, early re- reduced fecundity or less fit larvae. After parturi- search was principally on systematics and basic tion, early life history stages of Sebastes are plank- biology, whereas studies in fisheries and ecology tonic, in some cases in excess of 1 year. The effects have increased over recent decades (Fig. lb). A of environmental variation on reproduction and major goal of the seminar on reproduction and the role of the maternal system in post-Parturition ecology of early life history in Sebastes was to join survival is thus an important concern. 11 the separate strengths of U.S. and Japanese in- N. America I vestigators. Japan EZ The role of fisheries in research on Sebastes in North America began on the east coast, where depleted stocks of redfish, S. marinus, led to con- vening one of the first international symposia on the genus (Trout 1961). As west coast fisheries on rockfish took on increasing importance, directed fisheries research on Sebastes developed (Phillips 1964). The abundance of larvae was recognized as important from early studies of the California Cooperative Oceanic Fisheries Investigations (Ahlstrom 1961). Ecological studies arose from the many species of Sebastes and their importance in coastal ecosystems, particularly on the west coast, resulting in studies on all phases of the life history: ecology of pelagic larvae and juveniles (Ahlstrom 1961, Moser & Ahlstrom 1978), reproduction (Moser 1967, Boehlert & Yoklavich 1984), behav- ior and ecology of adults (Larson 1980) and ecology and energetics of benthic juveniles (Boehlert & Yoklavich 1983). The importance of many

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