Status of the Chilipepper rockfish, Sebastes goodei, in 2007 John C. Field Groundfish Analysis Team Fisheries Ecology Division Southwest Fisheries Science Center 110 Shaffer Rd. Santa Cruz, CA 95060 [email protected] EXECUTIVE SUMMARY Stock Structure: This assessment applies to the chilipepper rockfish (Sebastes goodei) in the waters off of California and Oregon, in the region bounded by the U.S./Mexico border in the south through the Columbia River in the north. Although the distribution is described in the literature as ranging from Queen Charlotte Sound (British Columbia) to Bahia Magdalena (Baja California Sur), the region of greatest abundance is found between Point Conception and Cape Mendocino, California. Catch History: Chilipepper rockfish have been one of the most important commercial target species in California waters since the 1880s, as well as an important recreational target in Southern California waters historically, and an important recreational target in central and northern California more recently (following the movement of recreational fishing effort to deeper waters in the 1970s and 1980s). Catches were estimated to have begun in 1892, and are estimated to have ranged from several hundred to nearly 1000 tons throughout the first half of the 20th century. Gear types are grouped into four general categories; trawl, hook and line, setnet, and recreational; since World War II a majority has been taken with trawl gear, although hook and line, setnet, and recreational gear have accounted for between 20 and 40% of landings for most of the last three decades. As early rockfish landings were only reported at the genus level, a combination of historical data and publications, as well as anecdotal accounts of early line, trawl, and recreational fisheries, were used to reconstruct the fraction of catch by gear and sector assumed to be chilipepper. Estimated landings from foreign fisheries from the mid-1960s through the mid-1970s were included as part of the trawl fishery. Throughout most of the past three decades, domestic landings have ranged between approximately 2000 and 3000 tons, however since 2002 landings have averaged less than 100 tons per year (Table E1, Figure E1), primarily a consequence of area closures implemented to rebuild depleted co-occurring species such as bocaccio (S. paucispinis) and canary (S. pinniger) rockfish. Discards are assumed to be negligible in the historical period, however regulatory discards have been substantial in recent years, more than doubling the total catch relative to landings since 2002. Table E1: Recent commercial and recreational landings (mt, excludes discards) Year Trawl Hook/line Setnet Recreation 1995 1595 325 94 7 1996 1528 254 58 30 1997 1614 339 83 73 1998 1138 209 78 5 1999 839 104 10 24 2000 403 51 6 39 2001 436 25 5 52 2002 162 3 0.2 12 2003 18 0.2 0.1 0 2004 61 3 1 6 2005 60 3 0.1 4 2006 37 6 0.2 1 1 recreational 5000 foreign net hookline trawl 4000 3000 2000 total chilipepper catch (tons) 1000 0 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 Figure E1: Estimated catches of chilipepper rockfish by major fishery Data and Assessment: Chilipepper rockfish were last assessed in 1998 (Ralston et al. 1998), at which time they were considered to be above target levels of abundance. From 1978 through 2006, commercial catches and demographic (age and length composition) data for California were obtained from the CalCOM database, those from Oregon were obtained from the PacFIN database, and recreational catches and length composition data were obtained from the RecFIN database beginning in 1981 (with interpolation of landings in missing years). Indices of relative abundance used in the assessment model included a catch per unit effort index from commercial trawl logbooks (from 1980 to 1996, developed and used in the 1998 assessment), an index of relative abundance from a recreational observer program (1987-1998), an index of relative abundance based on the triennial trawl survey (1980-2004), an index of relative abundance based on the Northwest Fishery Science Center Combined Survey (2003-2006), and a coastwide index of pelagic age-0 juvenile abundance developed by combining data from both the SWFSC and NWFSC/PWCC juvenile survey data. Several other potential sources of information were evaluated in earlier models and are discussed in the assessment documentation, although they were not used in the final model. The population was modeled using an age and size structured statistical model, Stock Synthesis II (SS2), version 2.00c, the modeling framework used for most West Coast groundfish assessments. Unresolved Problems and Major Uncertainties The length composition data were down-weighted when associated age-composition data were available, however the approach was acknowledged to be ad-hoc. A more appropriate approach 2 is to use conditional age-at-length compositions, which should be explored in more detail in future modeling efforts. The results from the convergence tests with randomly jittered starting parameter values indicated that the likelihood surface is very irregular. In general, biomass trajectories and other critical results do not appear to be sensitive to these differences. The application of a combined age- and length- based selectivity curve for the recreational CPFV data is somewhat non-traditional and would benefit by either more detailed investigation or an alternative selectivity configuration (an age-based, sex-specific selection curve showed considerable promise). Future (post-1999) year class strength is highly uncertain; although this model includes highly influential projections through 2006 based on juvenile abundance indices, the failure of the historical (core area) juvenile index to capture much of the year class variability that has been observed is cause for some concern. The current approach for implementing time-varying growth would benefit by additional data (particularly fishery-independent size at age data), the use of conditional age-at-length data, and more comprehensive efforts to link variability in growth to climate conditions. Stock Status: This assessment estimates that the spawning biomass of chilipepper rockfish (Sebastes goodei) has increased substantially in recent years, due to a strong 1999 year class as well as greatly reduced harvest rates in commercial and recreational fisheries. The base model result suggests a spawning biomass of 23,889 tons in 2006, corresponding to approximately 70% of the unfished spawning biomass of 33,390 tons and representing a near tripling of spawning biomass from the estimated low of 8696 tons (26% of unfished) in 1999 (Figure ES-1). As both commercial and recreational fisheries for chilipepper rockfish have been greatly reduced in recent years due to management measures implemented to rebuild depleted rockfish, it is likely that the stock will continue to increase modestly in the longer term under assumptions of equilibrium recruitment. Table E2: Recent trends in chilipepper rockfish spawning biomass and relative depletion year 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 Summary biomass 17008 16453 15865 14578 13635 13573 18556 23175 27023 30022 31509 32405 32401 Spawning biomass 9812 9589 9489 8968 8666 9029 9536 12671 17040 20229 22146 23224 23827 ~95 confidence limits on spawning biomass lower 8418 8033 7743 7046 6608 6734 7044 9281 12336 14616 15984 16773 upper 11259 11202 11296 10953 10785 11379 12080 16125 21830 25948 28424 29797 depletion 0.29 0.29 0.28 0.27 0.26 0.27 0.29 0.38 0.51 0.61 0.66 0.70 0.71 ~95 confidence limits on depletion lower 0.25 0.24 0.23 0.21 0.2 0.2 0.21 0.28 0.37 0.44 0.48 0.5 upper 0.34 0.34 0.34 0.33 0.32 0.34 0.36 0.48 0.65 0.78 0.85 0.89 3 Figure E2: Estimated trajectory of spawning stock biomass over the modeled period. Recruitment An extremely strong 1999 year class represents the largest estimated historical recruitment, and is the primary cause for the current population trajectory. A year class of comparable strength was also observed in 1984, and the model suggests a series of strong year classes in the late 1960s and early 1970s as well. There are no obvious signs of strong year classes since 1999, and coastwide pelagic juvenile surveys suggest average to low recruitment in recent years, suggesting that the stock may dip slightly in the near term. The projected low recruitments in 2005 and 2006 are based exclusively on the coastwide pelagic juvenile rockfish survey index, which is of short duration and has yet to be validated. Table E3: Estimated recruitment (1000s) for the recent (1995-2006) period year 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 recruits 15080 6555 7584 12569 153415 3708 15148 23831 14082 25895 7647 6645 32063 ~95 confidence limits on recruitment lower 8031 1399 2723 4260 104994 0 9036 14220 8380 15385 4546 3959 upper 22095 11691 12465 20936 202966 8023 21322 33540 19842 36511 10779 9358 4 Figure E3: Estimated recruitment over the modeled time period Exploitation Status: Although chilipepper rockfish have been a commercially important species in California waters since well before the second World War, the exploitation rate has rarely exceeded the current target exploitation rate (SPR 50%). The highest exploitation rates occurred from the late 1980s through the mid 1990s, when they were above target levels and the stock was approaching it’s lowest estimated historical levels. From the late 1990s through the present, exploitation rates have been declining significantly, as a result of management measures implemented to rebuild other depleted rockfish species. Table E4: Estimated exploitation rate (catch/sum bio) for the recent historical period Year 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 Expl.