hydroacoustic and midwater trawl segment of the rockfish survey) Ma­ Shortbelly Rockfish, Sebastes jordan;: l son ). A Large Unfished Resource in Preparation of this paper was Waters Off California prompted by the interest shown by both fishermen and processors in developing a fishery for shortbelly rockfish. The WILLIAM H. LENARZ objectives of the paper are to sum­ marize information on the species and: I) Describe the biology of the species, 2) make first approximations of the reaction of the stock(s) to various levels Introduction objects such as reefs or kelp more often of fishing, 3) review the rockfish survey than most, if not all, Cal ifornia rep­ results with regard to fishing, 4) review The shortbelly rockfish, Sebastes resentatives of the genus. Occasional potential of a fishery, and 5) discuss jordani, is one of the more distinctive catches have been made by purse sein­ management options for the fishery. members of the 57 species of rockfish ers fishing in southern California wa­ (genus Sebastes) which are reported ters, and the species predominated in Biology from California waters. The species ob­ midwater and demersal trawl catches of tains its common name from the fact rockfish off central California in the Larval and Juvenile Stages that its vent is about midway between 1977 rockfish survey (Gunderson and Moser et al. (1977) summarized the origin of the anal fi n and insertion of Sample, 1980). available information on larval and the pelvic fin, while the vent of other Shortbelly rockfish have been re­ juvenile stages of shortbelly rockfish. species of rockfish is located farther ported from San Benito Island, Baja The larvae are released at an average back, much closer to the origin of the California, Mexico (Moser et aI., 1977) size of 5.4 mm by the ovoviviparous anal fin. The shortbelly rockfish also to La Perouse Bank, British Columbia females between January and April. has a more strongly incised tail and a (Miller and Lea, 1972). Miller and Lea Larvae were collected between north­ more fusiform shape than most also report maximum depth as 283 m ern Baja California, Mexico, and as far rockfish. (155 fathoms) and maximum total north as San Francisco, Calif. Their Moser et al. (1977) noted that larvae length as 305 mm (12 inches). samples were not taken north of San of shortbelly rockfish are the longest at While there is no fishery for Francisco. While larvae were collected birth of eastern Pacific rockfish studied shortbelly rockfish, the species appears as far as 278 km (150 miles) offshore, to date. Also, the larval period is long to be very abundant in California wa­ all above-average catches were taken prior to transformation to the juvenile ters. Moser et al. (1977) estimated that much closer to shore. They also re­ stage when compared with other east­ larvae of shortbelly rockfish composed ported that larvae metamorphose to ern Pacific rockfish. These features, in 20 percent of all rockfish larvae taken in juveniles at 27 mm and appear to begin addition to the pigmentation pattern and a sampling program off southern forming schools at the surface at that morphometrics of young larvae, are California and 12 percent off central time. Juveniles up to 62.8 mm have remarkably similar to those of the California in 1966. While the catch of been taken by dip nets under night redfish or ocean perch, S. marinus, shortbelly larvae compared with all lights. On the other hand, specimens as group of the Atlantic Ocean. rockfish larvae was higher off southern small as 70 mm were taken by bottom Another distinction of adult California than central California, the trawling during the rockfish survey. shortbelly rockfish is that it occurs in catch per standard haul was higher off midwater and away from underwater central California (4.22 larvae) than Growth southern California (2.65 larvae). The Shortbelly rockfish, while being one biomass in a limited area of its range, of the smaller species of rockfish, has William H. Lenarz is with the Tiburon Labora­ between Pt. Ano Nuevo and Pt. San the highest rate of growth completion tory, Southwest Fisheries Center, National Marine Fisheries Service, NOAA, 3150 Paradise Pedro, was estimated to be 295,000 (k) of 10 California species studied by Drive, Tiburon, CA 94920. metric tons (t) from the results of the Phillips (1964). The von Bertalanffy ABSTRACT-Shortbellyrockfish, Sebas­ imations ofthe effect offishing on the stock, 'Mason, 1. E. 1978. Preliminary report on the tes jordani, appear to be abundant in 3) a review of the rockfish survey results hydroacoustic/midwater trawl survey for rockfish conducted off parts of the American and Cana­ to 4) California waters and present the potential with regard fishing, a review of the dian west coasts during July 12-September 30, for development ofa new largefishery in the potential for development of a fishery, and 1977. Unpubl. manuscr., 6 p. Northwest and area. This paper contains: 1) A description 5) a discussion of management options for Alaska Fisheries Center, NMFS, NOAA, 2725 ofthe biology ofthe species, 2)first approx- the fishery. Montlake Blvd. E., Seattle, WA 98112. 34 Marine Fisheries Review growth curve was used to describe fish from several sources and evalua­ growth: tion of selectivity is not possible. Data Females from the surveys (Fig. 2) indicated that = -k(f-f ») L f L x(l-e O 28 females grow larger than males and at­ Moles tain maximum size at a slower rate of where L f = total length (mm) at t, 24 completion (lower k). Growth does not t = age in years, appear to be related to depth ofcapture, k = growth completion 20 but there are insufficient data from the rate, survey to arrive at conclusive results. to= theoretical age when Length-Weight fish is length 0, and The length-weight relationship was Lx = estimate of average estimated by Phillips to be log W = length attained at a +{3logL, where W = weight in maximum age. pounds, L = total length (mm), a = -8.05202, and {3 = 3.1518. Phillips combined age-length data from Maturation, Fecundity, and both sexes and made his estimates from 1 2 3 " 5 6 7 8 9 10 Sex Composition back-calculated lengths (estimates of Age (yeors) length at time of formation of each an­ Phillips (1964) reported that 50 per­ nual ring on a scale) made from scale cent of shortbelly rockfish "... are Figure I.-Von Bertalanffy growth readings and measurements. He as­ mature when 6Jh inches [16.5 cm] curves for Sebastesjordani estimated long, or 3 years old." The fecundity­ sumed that scales form at birth. My from this study and by Phillips experience with several other species of (1964). length relationship, estimated by me rockfish indicates that scales form when from Phillips' data on to specimens is the fish reach about 20 mm. Thus the In F = a + /3lnL, where F = fecundity back-calculations of Phillips probably (numbers of eggs), L = total length slightly under-estimate lengths of (mm), a = -8.43523, and f3 = 32 young fish. 3.30611. Additional data on growth are avail­ About 45 percent of the survey 2. able from the rockfish survey. Otoliths catches of shortbelly rockfish between from 1,081 specimens were read. 14 cm and 27 cm were males. Few of Opaque zones of fast growth were just 2' the fish larger than 27 cm were males. beginning to be formed at the time of 20 Movements sampling (midsummer). Phillips' ~ back-calculations appear to be at the .c While many aspects of the life his­ '"e I. end of the growth season (midwinter). ~ tory of shortbelly rockfish appear in the ;; Thus fish from the rockfish survey ~ literature, nothing could be found on should be 0.5 year older than those Phil­ 12 movements. Tagging studies on blue lips used. Phillips used total lengths, rockfish, S. mystinus, Miller and while fork lengths were measured for Geibel (1973); yellowtail rockfish, S. the rockfish survey. Total length is flavidus, Carlson and Haight (1972); about 15 mm greater than fork length copper rockfish, S. caurinus, Dewees for shortbelly rockfish, and the survey (1970); and black-and-yellow rockfish, data were adjusted accordingly. The <l 5 7 8 9 10 S. chrysomelas, and gopher rockfish, program BGC2 (Abramson, 1971) was Age (yeors) S. carnatus, Hallacher (1977) and Lar­ used to estimate parameters of the son (1977) indicated little movement. growth curve. The estimate ofk for the Figure 2.-Von Bertalanffy growth However, these five species do not have survey data, 0.27721, is very close to curves for female and male Sebastes strongly incised tails or fusiform the estimate by Phillips, 0.27520. The jordani. L x is 324 mm for females bodies. These aspects of morphology estimates of L x are also close, 315 and 290 mm for males; k is 0.2112 for females and 0.2980 for males. would suggest that shortbelly rockfish (Phillips) and 30I (survey). Compari­ are stronger swimmers and are better son of the two growth curves (Fig. I) adapted to swim away from predators reveals that the main differences occur and/or make more extensive move­ at young ages. As previously men­ mesh size of the nets used by the survey ments than the other fi ve species (Hob­ tioned, Phillips probably underesti­ may have selected for relatively large son and Chess, 1978). Analyses of mated length offish at young ages. Also fish at young ages. Phillips obtained catch rates of Pacific ocean perch, S. March-April 1980 35 alutus, indicate considerable move­ ment into relatively shallow waters dur­ ~228m ing spring and summer and return to LN.44'59'N deeper water in the winter (Gunderson, '::UL C C 1972).