The Feasibility of Enhancing Red Sea Urchin, Strongylocentrotus franciscanus, Stocks in California: An Analysis of the Options MIA J. TEGNER Introduction tially throughout the range of the fish­ Ui 25,000 ery, the alternatives are a reduced c: B 20,000 The red sea urchin, Strongylocen­ harvest and contraction of the indus­ .!'! ~ 15,000 trotus franciscanus, is the largest try, or stock enhancement to maintain §. echinoid in kelp forest communities populations above what is possible ~ 10,000 c: along the west coast of North America with current fishery practices. The =g 5,000 C\l and is fished commercially from Brit­ spectacular successes achieved with ...J o+--..:.....~---.---~~~ ish Columbia to Baja California some finfishes, notably the salmonids, 1970 1975 1980 1985 (Sloan, 1986). The California sea as well as the many recent advances in Figure I.-California landings of urchin fishery began in the early aquaculture, have led to widespread red sea urchins, 1971-87 (Calif. 1970's and grew very rapidly to total interest in the second and more eco­ Dep. Fish Game. Unpubl. data). landings of more than 20,000 metric nomically appealing alternative. Here, tons (t) in 1987 (Kato and Schroeter, I examine potential options for the en­ l 1985; Parker ). By 1987, this was the hancement of red sea urchin stocks, second most valuable fishery in Cali­ consider the conditions under which methods to enhance fishable stocks. fornia waters with a landed value of each might be appropriate, and make The success of all attempts to enhance $13,693,000. There are no unfished relative estimates of the costs and ef­ benthic invertebrate stocks by the re­ stocks left in southern California; only fort involved. lease of hatchery-reared juveniles will the development of a northern coastal The concept of stock enhancement be reviewed, as well as other methods fishery in the mid 1980' s allowed for valuable invertebrate fisheries is relevant to sea urchins. Because the the continued increase in landings not new. Transplantation of abalones, success of many Japanese approaches (Fig. 1). Haliotis spp., to better habitats for is related to the structure of their fish­ With the eventual elimination of un­ growth dates to the 19th century (lno, ing industry, this and the implications fished stocks statewide, and poten- 1966), and lobster, Homarus spp., of the American tradition of open­ juveniles were cultured for release on access fisheries for stock enhancement fishing grounds as early as the 1880's will be discussed. I D. Parker, Calif. Dep. Fish Game, 330 Golden (Van GIst et aI., 1980). The Japanese The success of any enhancement ef­ Shore #50, Long Beach, California 90802. Unpub!. data, 1989. in particular have explored a variety of fort will depend upon the answer to a critical question: What stages in the life history of the organism limit the production of fishable stocks? For red ABSTRACT-The California fishery for the extensive Japanese work, to enhance sea urchins, the limiting factors could red sea urchins, Strongylocentrotus fran­ fishable stocks of benthic marine inverte­ be larval supply, problems associated ciscanus, has undergone explosive growth brates, and consider the potential options with settlement, survival of newly set­ in recent years and is approaching full for red sea urchins at different points of exploitation. Thus, there is considerable limitation. These include collecting or cul­ tled to mid-sized animals, or adequate interest in enhancing stocks to maintain a turing seed for outplanting, physical habi­ high rate of landings. Fishable stocks of tat improvement measures, improving the Mia J. Tegner is with the Scripps Institution of red sea urchins in different areas appear to food supply, and conservation measures to Oceanography, A-OO I, University of California, be limited at three stages in their life his­ protect existing stocks until alternate San Diego, La Jolla, CA 92093. Mention of tory: By the availability of larvae, by the methods are proven and in place. The op­ trade names of commercial firms in this paper survival of newly settled to mid-sized ani­ tions are compared in terms of biological does not imply endorsement by the National Marine Fisheries Service, NOAA. Views or mals, and by the food available to support feasibility, capital and labor requirements, opinions expressed or implied are those of the growth and reproduction of larger ani­ and potential implications for change in author and do not necessarily represent the posi­ mals. Here / review other efforts, notably the structure of the fishing industry. tion of the National Marine Fisheries Service. 5/(2), 1989 food to support growth and/or gonad reported from late spring to early sum­ was highest on the southeastern is­ production. Enhancement efforts mer or even fall. The length of the lands, those most affected by the which do not address the stage which planktonic larval phase is temperature Southern California Eddy, the closed limits production are not likely to be dependent. Strathmann (1978) re­ gyralcirculation of Parrish et al. successful; e.g. seeding of juveniles ported a range of 62-131 days for (1981), which appears to aid in the will do little for a population limited larvae cultured at ambient tempera­ retention of larvae, and was very low by survival of mid-sized animals or tures (generally 7°-l30 C) in Friday on the northwestern islands until the food supply. Furthermore, these fac­ Harbor, Wash., and Cameron and 1982-84 EI Nino when upwelling tors are likely to vary on local and Schroeter (1980) found the earliest rates were extraordinarily low. While regional scales, e.g. the survival of settlement at 40 days and the peak at little red sea urchin recruitment data is mid-sized animals correlates nega­ 50 days after fertilization for larvae available from the region of maximum tively with the abundance of two warm cultured at l20 e. Whatever the tem­ upwelling, it is reasonable to assume temperate predators, spiny lobsters, perature, the length of the planktonic that stocks in central and northern Panulirus interruptus, and California phase indicates that the distribution of California are more likely to be limited sheephead, Semicossyphus pulcher the larvae is strongly affected by cur­ by larval supply than those in southern (Tegner and Dayton, 1981; Tegner and rent patterns. California. Barry2). The northern range limit of Current patterns, and thus the fate of The settlement requirements for red these two predators is normally Point sea urchin larvae, vary seasonally and sea urchin larvae are poorly under­ Conception, and both are character­ with latitude. Parrish et al. (1981) di­ stood. Hinegardner (1969) reported istic of bottoms with considerable ver­ vide the California Current System that both red and purple sea urchin tical relief; they will have little impact into four oceanographic regions on the larvae settle on an algal and bacterial on red sea urchins north of southern basis of mean geostrophic flow, film. Cameron and Schroeter (1980) California or in pavement habitats. Ekman transport, and wind stress curl observed no substrate specificity Finally, enhancement methods will patterns. California falls into two of among several filmed natural sub­ vary considerably in costs, in the these regions, the region of maximum strates and suggested that sea urchin length of time required to achieve re­ upwelling from Cape Blanco to Point larvae settle on any surface they en­ sults, and in how long the results will Conception which includes the north­ counter once they became competent last. western Channel Islands, and the to undergo metamorphosis. Rowley Southern California Bight. The region (1989) found that purple sea urchin Summary of the Life History of maximum upwelling is character­ larvae settle at significantly higher of Red Sea Urchins ized by strong offshore surface trans­ rates in response to crustose coralline The biology of S. franciscanus has port during the spring and summer, algae and red algal turf than in re­ recently been reviewed by Kato and whereas the Southern California Bight sponse to filmed rocks, but was not Schroeter (1985). Here I will sum­ is an area of minimal upwelling and a able to demonstrate density differences marize aspects of the life history rele­ closed gyral circulation (Parrish et aI., among natural substrates for newly vant to factors potentially limiting the 1981). These oceanographic patterns settled « I mm) red sea urchins. size of fishable stocks. appear to have major implications for Thus, evidence to date suggests that The timing and length of the spawn­ the transport of larvae. The Southern suitable substrates for settlement are ing season of red sea urchins are California Bight, the area of minimal not likely to be limiting as long as highly variable among locations (Kato upwelling, has the highest known rates excessive sedimentation or pollution and Schroeter, 1985). Seasonality may of red sea urchin recruitment (to the are not an issue. be related to the patterns of food avail­ population) throughout its range In contrast, the survival rates of ability (Bernard, 1977); red sea ur­ (Sloan et aI., 1987). Ebert and Russell newly settled to mid-sized animals do chins in the Point Loma kelp forest (1988) report reduced recruitment of appear to limit the size of fishable near San Diego, where food is gen­ intertidal purple sea urchins (S. pur­ stocks in some populations. While red erally abundant, are thought to spawn puratus) on headlands, predictable sea urchin larvae do not settle in re­ throughout the year although there is a sites of upwelling, compared with sponse to adults (Cameron and winter peak. North of southern Cali­ areas without predictable upwelling Schroeter, 1980), juvenile abundance fornia, where food may be primarily within the region of maximum upwell­ is often highest underneath the test or available from mid spring to mid fall ing.