Diversity and Ecological Roles of Noncommercial Fishes in California Mar1 N E Habitats
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HORN: DIVERSITY AND ECOLOGICAL ROLES OF NONCOMMERCIAL FISHES CalCOFI Rep., Vol. XXI, 1980 DIVERSITY AND ECOLOGICAL ROLES OF NONCOMMERCIAL FISHES IN CALIFORNIA MAR1 N E HABITATS MICHAEL H. HORN Department of Biology California State University Fullerton. CA 92635 ABSTRACT habitat ocupado por 10s peces de importancia economica. The marine fish fauna of California is highly diverse Las especies que no son comerciales pueden funcionar and consists of about 550 species of varied origin and como 1) predadores o presas, asi son eslabones troficos complex distribution. Species richness is greatest in directos en la cadena alimenticia de las especies comer- southern California and gradually declines northward in a ciales; 2) competidores de las especies explotadas; 6 3) pattern that is significantly correlated with increasing peces que, por su posicion ecologica, afectan la estructura latitude and decreasing minimum surface temperature. de la comunidad e influyen indirectamente en las pobla- Greater activity with regard to species range termina- ciones de importancia economica. tions occurs in southern California than in central and Se describe brevemente las comunidades de peces y northern California and is consistent with the higher ciertas especies de importancia ecologica para cada uno species richness in southern California waters. de 10s siete habitats mas importantes en las aguas Less than 3% of the species of this diverse fauna con- oceanicas de California: 1) zona profunda mesopelagica, tributes significantly to the California commercial fish 2) zona epipelagica, 3) region demersal costera, 4) lechos catch. Many noncommercial species, therefore, perform de algas marinadarrecifes sublitorales, 5) zona de entre essential roles in the habitats occupied by economically mareas rocosa, 6) puertos, y 7) bahias y estuarios. En las important fishes. The noncommercial species may func- conclusiones se seriala que las bahias y estuarios son tion as 1) predators or prey, thus as direct trophic links in importantes, per0 estos habitats se alteran y por eso the food chain of commercial species; 2) competitors of necesitan cuidados para conservarlos. exploited species; or 3) fishes which otherwise, by their ecological position, affect community structure and in- INTRODUCTION directly influence economically important populations. A primary purpose of this paper is to focus attention on The fish communities and certain ecologically impor- the diversity and complexity of the California marine fish tant species are briefly described for each of seven major fauna especially beyond the relatively small number of habitats in California marine waters: 1) deep midwaters, species that contribute to the commercial catch. Non- 2) epipelagic zone, 3) coastal demersal region, 4) kelp commercial forms have both direct and indirect relation- bedshubtidal reefs, 5)rocky intertidal zone, 6) harbors, ships with economically important species. The “other” and 7) bays and estuaries. Bays and estuaries are em- fishes may be predators or prey of exploited species, phasized in the concluding statements as important but competitors of commercial species, or in other ways diminished and altered habitats in need of preservation affect community structure and secondarily influence 2nd wise management. economically important populations. In this account, the fish communities are briefly described and the roles of ecologi- RESUMEN cally important and interesting species emphasized in seven La fauna de peces marinos de California es sumamente major marine habitats: 1) deep midwaters; 2) epipelagic diversa y comprende unas 550 especies que proceden de zone; 3) coastal demersal region; 4) kelp bedshubtidal reefs; varias regiones y que presentan una distribucion com- 5) rocky intertidal zone; 6) harbors; and 7) bays and pleja. La riqueza en especies es mayor en el sur de estuaries. California y disminuye gradualmente hacia el norte siguiendo un patron que se relaciona con la latitud y el DIVERSITY AND DISTRIBUTION PAlTERNS OF descenso en la temperatura minima de las aguas de CALIFORNIA MARINE FISHES superficie. En el sur de California se encuentran mas The fishes occurring off the coast of California com- limites de zonas de distribucion de las especies que en el prise a rich fauna of varied origin and complex distri- centro y norte de California, lo cual concuerda con el bution. As recently shown by Horn and Allen (1978), mayor numero de especies que habitan las aguas del sur de diversity (number of species) is greatest in southern Cali- California. fornia gradually declining northward to Alaska in a pat- Menos del 3% de las especies de esta fauna diversa tern that is highly correlated with increasing latitude and contribuyen a la captura comercial de 10s peces de decreasing minimum surface temperature. The steep de- California. Por lo tanto, muchas especies que carecen de cline in the number of California fishes occurring off Baja valor comercial desempenan un papel esencial en el California and southward is apparently related (Horn and 37 HORN: DIVERSITY AND ECOLOGICAL ROLES OF NONCOMMERCIAL FISHES CalCOFI Rep., Vol. XXI, 1980 tions, especially of temperature in the Point Conception area (Figure I), are apparently more critical for southern species than for northern ones. Miller and Lea (1972) listed 554 species as occurring L off California. Of these, 439 are found in coastal waters 100 w o MAX. TEMP. 18 I- (<- 120-m depth), 48 in meso- and bathypelagic zones .MIN. TEMP. UY (about 25% of the total midwater fauna), and 67 benthic RANG€ END POINTS I4 2 0 NORTHERN a m forms found at depths greater than 120 m. Eleven families SOUTHERN IO account for 256 species (46%) of Miller's and Lea's (1972) total list (Table 1). This group of families illus- 6 trates the multiple origins of the fauna since it includes 36 families of temperate affinities (Cottidae, Pleuronectida, 20 Embiotocidae, and Agonidae), of tropical-subtropical rela- tionships (Scombrida, Carangid=, Gobiidae, Clinidae, Carcharhinidae, and of deepwater origin (Myctophida). 45 Nb LATITUDE Scorpaenidae is primarily a family of tropical affinity, Figure 1. Frequency of northern and southern end points of geographic although the subfamily Sebastinae (containing the diverse ranges of 499 California coastal fish species at each degree of latitude over genus Sebustes) has a temperate-boreal distribution. the total distributional range (2 30"s to2 60"N. The bars representingthe number of northernand southern end points originate at the basal line. The bars for northern and southern values at 32"N are reversed in position relative to other latitudes because the open (northern) bar represents a smaller value than the black (southern) bar only at this latitude. Maximum COMPOSITION OF THE CALIFORNIA and minimum surface temperatures are derived from monthly meansforthe COMMERCIAL FISHERY 14-Year period 1949-62. (All data from those compiled by Horn and Allen 1978.) Only a small percentage of California species occur in the commercial catch. No more than about 120 species are among the annual landings and shipments in Cali- Allen 1978) not only to changing oceanographic condi- fornia (e.g. McAllister 1976). However, most of these tions but to competition with the large tropical fauna species are rarely captured or otherwise contribute insig- south of California that is greater than that with the small nificantly to the total catch. The California commercial boreal fauna which occurs north of California. The distri- fishery is overwhelmingly dominated by pelagic wetfish bution of range end points of California fishes (Figure 1) (northern anchovy, Engruulis mordux, and jack mack- serves to emphasize the richness and multiple affinities erel, Truchurus symmetricus) and tunas (Table 2). The (especially northern and southern) of the fauna and to tunas, mainly yellowfin (Thunnus ulbacures) and skip illustrate the relationship of diversity to surface sea temp- jack (Euthynnuspelamis), are primarily caught in tropi- eratures. Frequency of both northern and southern ter- cal waters outside of California (e.g. about 94% of the minations of species ranges are bimodal in pattern with 1972 catch, Bell 1974). Trawl fisheries are relatively the proximal modes of each occurring in southern Cali- more important from Santa Barbara northward but con- fornia. The high concentration of range terminations in southern California is to be expected since it is the region TABLE 1 of greatest species richness. Increased diversity in south- The 11 Most Speciose Families of Fishes in California Waters.' ern California is probably related (Horn 1974) to en- Number of vironmental heterogeneity as expressed by the expansive Family Common name species borderland, the insular habitats adjacent to deep basins, and the converging water masses characteristic of the Scorpenida: Thomyheads, 62 scorpionfishes, rockfishes region. Cottida: Sculpins 42 Species with southern affinities tend to have northern Myctophida: Lantemfshes 32 range end points off southern California, and southem end Pleuronectidae Right-eye flounders 20 points off Baja California or much farther south off Cen- ,Ernbiotocidae Surfperches 19 tral or South America. Fishes with northern affinities Agonidae Poachers 17 Scombrida: Mackerels and tunas 15 most frequently have northern range end points at high Carangid= Jacks and pompanos 13 latitudes off British Columbia or Alaska and southern end Gobiidae Gobies 12 points off southern California and northern Baja Cali- Clinida: Clinids 12 fornia.