Population trend
Trend
Pterogymnus laniarius is considered to be on of the most abundant sparid species on the Agulhas Bank, South Africa (Booth and Buxton 1997b, Booth and Punt 1998). Based on data from a per-recruit analysis conducted in 1994-1995, the stock is considered to be under-exploited (Booth and Buxton 1997b, Booth and Punt 1998). Despite being subject to directed foreign trawl fleet effort between 1964-1991, with landings as high as 18,000 tonnes per annum (Crawford et al. 1987), P. laniarius appears to be showing evidence of a recovery (Booth and Punt 1998), with the possibility that increased catches would be sustainable (Brouwer 1997, Booth et al. 1999). At least 95% of the stock is located between Cape Agulhas and Port Alfred.
A 1.1% increase in catch per unit effort (CPUE) was observed between 1984 and 1995 from the demersal inshore trawlfishery (Booth and Hecht 1998). Similarly, CPUE in the commercial linefishery increased from 2 g/person/hour in 1989 (Clarke and Buxton 1989) to 3.3 g/person/hour in 1996 (Brouwer 1997). Since 1974, there has been a decrease in age-at-maturity and age-at-recruitment of the species caught as well as a decrease in mean size of fish landed in the demersal inshore trawl fishery in the Southeastern Cape (Booth and Griffiths 2000). Catches in the commercial linefishery increased from 1985 to a peak in 1992 of 270 tonnes and subsequently declined to 30–40 tonnes in 2001 where it has remained stable. Using targeted effort data, there was no significant upward or downward trend in abundance (CPUE) over a 25 year period since 1985 (NMLS unpublished data). More recently CPUE in the Port Alfred commercial linefishery decreased significantly from 0.62 kg/fisher in 1985 to 0.25 kg/fisher in 2007; however, this decline is suspected to be due to a change in fisher behaviour and economics as opposed to a decrease in actual stock abundance (Donovan 2010, Booth and Hecht 2012). The contribution of P. laniarius in the commercial linefishery catch in the Southeastern Cape has steadily declined from about 26% in the 1980s (Hecht and Tilney 1989, Booth and Buxton 1997b) to around 5% in 2007 (Donovan 2010).
Pterogymnus laniarius has been caught commercially since the early 1900s. This species has been an important part of the South African fishery and, from the 1950s to early 1970s, it constituted the third most important trawlfish species landed, despite being caught as bycatch. In 1964, a directed fishery was developed with the introduction of Japanese and Taiwanese trawlers to South African waters. Foreign catches peaked at the initiation of this fishery reaching 14,000 tonnes to 18,000 tonnes. From 1970, catches dropped averaging 10,000 tonnes until the introduction of an Exclusive Economic Zone in 1978 when the imposition of a small quota of 1,700 tonnes resulted in this species being caught as bycatch in the new horse mackerel directed fishery (Booth and Buxton 1997b). Foreign trawl fleets were completely excluded from South African waters by 1993. The annual catch (all sectors combined) over the past decade averages some 830 tonnes (Booth and Punt 1998).
Commercial data show that since 2000 commercial fishing effort has declined dramatically in the South African linefishery from approximately 3,000 to 450 vessels in line with the long-term fisheries rights allocation process implemented in 2006 (Department of Agriculture, Forestry and Fishery 2012).
