Characterisation and CPUE analyses of the flatfish fishery in FLA 3 M. P. Beentjes 1 M. J. Manning 2 1NIWA P O Box 6414 Dunedin 9059 2NIWA Private Bag 14901 Wellington 6241 New Zealand Fisheries Assessment Report 2010/27 September 2010 Published by Ministry of Fisheries Wellington 2010 ISSN 1175-1584 (print) ISSN 1179-5352 (online) © Ministry of Fisheries 2010 Beentjes, M.P.; Manning, M.J. (2010). Characterisation and CPUE analyses of the flatfish fishery in FLA 3. New Zealand Fisheries Assessment Report 2010/27. This series continues the informal New Zealand Fisheries Assessment Research Document series which ceased at the end of 1999. EXECUTIVE SUMMARY Beentjes, M.P.; Manning, M.J. (2010). Characterisation and CPUE analyses of the flatfish fishery in FLA 3. New Zealand Fisheries Assessment Report 2010/27 . The objective of this project was to characterise the FLA 3 fishery and analyse CPUE trends in the fishery. In addition, we also investigated ancillary data that included processor’s landings data, SeaFic logbook programme, and east coast South Island (ECSI) Kaharoa trawl surveys. The fishery characterisation data were extracted from the Ministry of Fisheries catch effort database Warehou from Catch Effort Landing Returns (CELRs) and Trawl Catch Effort Landing Returns (TCEPRs) for 1989–90 to 2006–07, and Net Catch Effort Landing Returns (NCELRs) for 2006–07, for statistical areas within FLA 3. The key features of the aggregated flatfish species fishery in FLA 3 include: 1) no strong seasonal trend in catch; 2) important statistical areas are those contiguous with the coast (020, 022, 024, and 026); 3) virtually all catch outside Te Waihora is taken by bottom trawl, and setnet within Te Waihora; 4) most of the flatfish catch was caught by vessels recording FLA (generic flatfish species code) as the target species with modest catches with target red cod (RCO), and lesser catches with target New Zealand sole (ESO) and lemon sole (LSO); 5) virtually all flatfish catch is landed from vessels completing CELRs (up to 2006–07); 6) the only three flatfish species caught in any quantity by trawling are ESO, LSO, and to a lesser extent sand flounder (SFL). Catches of these species are spread throughout the coastal statistical areas from 020 to 030, although LSO catch was greater in 026; 7) the setnet catch is virtually all from statistical area 022 (assumed to be Te Waihora), and the only species caught in any amount are black flounder (BFL), SFL, and yellowbelly flounder (YBF). Kaharoa ECSI trawl surveys indicate that LSO is the main flatfish species followed by ESO and SFL in winter, and ESO and greenback flounder (GFL) in summer. SFL inhabit the shallow coastal areas down to and probably inside 10 m, ESO predominantly in 10 to 30 m, with LSO extending deeper again into the mid, and occasionally, outer continental shelf. Although the Kaharoa trawl net and survey design are not optimised for flatfish species, the relative proportions of species may be reasonably well represented within the depth ranges surveyed. The Sanford’s data and logbook scheme flatfish species mix are consistent with this finding. The flatfish species length frequency distributions from the Kaharoa and industry logbook scheme are similar and there are some indications of modes that represent age classes. There are insufficient data to plot length frequencies by survey to look at recruitment strength. An algorithm was applied to the aggregated flatfish groomed and merged (rolled-up) dataset to estimate the proportion of each flatfish species in the generic coded FLA catch. Allocation was based on 1) the associated non-generic estimated catches for the associated fishing records or trip and 2) Sanford’s Ltd Timaru dataset of species-specific landing weight data collected from 1992–93 to 2000–01 and 2003–04 to 2007–08 (there were no data for 2001–02 and 2002–03). Standardised CPUE indices were obtained by fitting Generalised Linear Models to the imputed (generic FLA codes converted to species specific codes) dataset. Separate CPUE analyses were carried out, for the bottom trawl fishery (FLA, ESO, LSO, and SFL) and the Te Waihora setnet fishery (FLA, BFL, SFL, YBF). Trawl fishery CPUE analyses for all species combined and the three key species, ESO, LSO, and SFL show generally similar trends of increasing CPUE in the mid to late 1990s, followed by a steep decrease, after which ESO has a secondary peak about 2001–02 followed by a steep decline, LSO increases again after about 2003–04, and SFL fluctuates with no clear trend. The trawl CPUE analyses are characterised by large fluctuations from year to year, reflecting few year classes and a fishery that is highly recruitment driven. The CPUE trends for all three species are consistent with biomass trends from Kaharoa surveys, commercial landings in FLA 3, and processor’s catch data, providing evidence that the CPUE indices generated for these three species are a proxy for abundance. The setnet CPUE models are marked by large fluctuations in the annual CPUE indices with no clear trends, and wide confidence limits around the indices, the latter a reflection of having only about 7 participants in the fishery. Unlike the trawl CPUE indices, there are no proxies of abundance to compare with the setnet CPUE indices to test for plausibility. 3 1. INTRODUCTION The flatfish commercial fishery in New Zealand comprises eight species from four genera: four flounders (black flounder, Rhombosolea retiaria ; greenback flounder, R. tapirina ; sand flounder, R. plebeia ; yellowbelly flounder, R. leporina ), two soles (lemon sole, Pelotretis flavilatus ; New Zealand sole, Peltorhamphus novaezeelandiae ), plus brill ( Colistium guntheri ) and turbot, ( Colistium nudipinnis ) (Kirk 1989, Colman 1994, Ministry of Fisheries 2006). Witch ( Arnoglossus scapha ) is also caught, but is less desirable and seldom landed. The Management practise of combining flatfish reported landings from all eight species under the code FLA has made it difficult to monitor abundance or catch trends of individual species. It is understood that the proportions of each species vary within the reported catch among the four flatfish QMAs (FLA 1, FLA 2, FLA 3, and FLA 7), but the relative annual contribution of each species is unknown since there are no landings for individual flatfish species documented (Ministry of Fisheries 2008a). In status of the stocks, the 2008 plenary report states that because of highly variable recruitment and few year classes …”a constant catch at the level of the current TACCs is unlikely to be attainable or sustainable, nor would it allow the stock to move towards a size that will support the MSY” (Ministry of Fisheries 2008a). There is clearly a need to monitor the abundance of individual flatfish species. 1.1 Commercial fishery for flatfish About half of the total landed flatfish weight in New Zealand is caught in FLA 3 (Ministry of Fisheries 2008a), an area that includes Fishery Management Areas (FMAs) 3, 4, 5, and 6 (Figure 1). Annual landings in FLA 3 fluctuate more than two-fold and have averaged about 1700 t since 1986–87 (Figure 2). The TACC has never been exceeded and has been between 44% and 96% caught, but overall has averaged 66% caught since 1999–2000. The original TAC was set high because flatfish growth is fast and recruitment is variable, with the fishery relying on one or two year classes each year (Ministry of Fisheries 2008a). The high TACC has allowed fishers to take advantage of years when abundance was high (for example 1996–97), a management regime similar to that for red cod, a species which is also fast growing, has variable recruitment (Beentjes 2000) and similar cyclical peaks and troughs in catches. Although flatfish catches are not declining, there has not been a peak catch close to the TACC since 1996–97. It is difficult to gauge the effect of current fishing pressure on individual species and it is possible that although FLA 3 landings appear reasonably stable (accepting the inherent annual variability), individual species may be stressed. The eight species of commercial flatfish have distinct life histories with differences in distribution, growth rates, spawning behaviour, and biology (Colman 1994). To more effectively manage flatfish under the QMS, information on catches by individual species is required. The bulk of the FLA 3 commercial catch (95%) is taken by inshore bottom trawl (CELR) with about 5% from setnetting (data from Beentjes 2003). Insignificant amounts of soles, brill, and turbot are taken as incidental bycatch by deepwater trawlers and reported on TCEPRs. The bottom trawl flatfish catch is taken from the inshore (less than 70 m) coastline of the east coast South Island and Southland. The bulk of setnetting catch is thought to be from Te Waihora (Lake Ellesmere), though it is not possible to determine the definitive amount because there is no reporting statistical area specifically for Te Waihora and all catch has been reported against area 022 (Banks Peninsula-Canterbury Bight). However, in Otago statistical areas 024 and 026, 99% of all landed flatfish was taken by bottom trawling, hence it is highly likely that the setnet flatfish catch in statistical area 022 is all from Te Waihora. Further, discussions with fishers suggest that setnetting has seldom been used to target flatfish in FLA 3. All eight commercial flatfish species are caught in FLA 3. The dominant species caught by trawling are lemon sole (LSO) and New Zealand sole (ESO), followed by sand flounder (SFL), with smaller landings of greenback flounder (GFL), brill (BRI), turbot (TUR), and yellowbelly flounder (YBF) (Beentjes 2003). In Te Waihora, flatfish setnet catches include black flounder (BFL) and YBF, with lesser quantities of SFL (Clem Smith, commercial fisher, pers. comm.). 4 1.2 Commercial fishing gear Flatfish are caught in either standard multispecies trawls, or specialised flatfish target trawls.