Red List of South African Species

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Near Threatened (NT)
Assessors: Bruce Mann Colin Buxton Kent Carpenter
Facilitators: Claire Gorman Mia Comeros-Raynal
Reviewers: Barry Russell David Pollard

Rationale

Chrysoblephus anglicus is the fifth most important reef fish caught in the commercial line fishery off Kwazulu-Natal. There are no clear trends in CPUE, relative proportion in total linefish catch and mean size. However, a per-recruit stock assessment showed that the stock had "collapsed" according to the Marine Linefish Management Protocol, with SB/R = 17% (F=0). There is evidence that this species is becoming increasingly targeted in KwaZulu-Natal because of serial depletion of other preferred linefish species. The total commercial catch for this species has declined by ~70% from 1987-2007, nearing the threshold for a threatened category. It is an endemic species with a relatively narrow distributional range, and is a suspected protogynous hermaphrodite in which the sex ratio of the mature population has become skewed in favour of females and is increasingly targeted in KwaZulu-Natal. Per recruit stock assessments have shown a decline of at least 30% over the past 20-30 years based on estimated per recruit analyses at 17% (<25% is considered to be collapsed). However, major trends have not been observed and there are multiple management measures in place for this species. Therefore, despite a major reduction, this species is listed as Near Threatened (A2bd).

Distribution

Chrysoblephus anglicus is endemic to the area between the mouth of the Limpopo River, in southern Mozambique, and Algoa Bay in South Africa (Bauchot and Smith 1984, Smith and Heemstra 1986, Heemstra and Heemstra 2004) with the main stock assumed to occur between southern Mozambique and the former Transkei (van der Elst and Adkin 1991). This species has a depth range of 10 to 120 m (Garratt et al. 1994).

Population trend

Trend

The C. anglicus stock is considered to be collapsed with a spawning biomass per recruit estimated at ~17% (Mann et al. 2005). A slight increase in catch per unit effort (CPUE) was observed from 58 kg per man per year (1940–1941) to 64 kg per man per year (1985–1992) (Garratt et al. 1994). As a proportion of the total commercial KwaZulu-Natal line fish catch, this species increased from 1.5% for the period 1940 to 1941 to 6% for 1985 to 1992 (Garratt et al. 1994). Mean size decreased slightly from 35 cm FL (1979–1981) to 34.3 cm FL (1990-92) (Garratt et al. 1994) but increased back to 35 cm FL in 2003 (Mann et al. 2005). Reported commercial catches of C. anglicus increased slightly in standardized CPUE from 0.28 kg per man per hour in 1985 to 0.34 kg per man per hour in 2007 (National Marine Linefish System unpublished data). The total commercial catch for this species has declined from a peak of about 70 tonnes in 1987 to an average of about 20 tonnes from 2004–2007. Using targeted effort data, there was no significant upward or downward trend in abundance over a 25 year period since 1985.

Male:Female sex ratio recorded on the KwaZulu-Natal south coast in 2003 (1:25, Mann et al. 2005) had changed from 1:14 recorded by Garratt et al. (1994). Differences in M:F sex ratios observed along the KwaZulu-Natal coast suggest that more male fish occur in the northern areas (e.g. 1:3.7 north of Richards Bay) compared to 1:14 south of Ramsgate (Garratt et al. 1994). Similarly, the mean size of fish sampled at Richards Bay (39.1 cm FL) were significantly larger than those sampled on the KwaZulu-Natal south coast (35 cm FL) (Mann et al. 2005). Male: Female sex ratio in St Lucia Marine Reserve was reported to be 1:3.7 while it was 1:4.0 on KwaZulu-Natal south coast (Fennessy et al. 2000). This species is an unconfirmed protogynous hermaphrodite with an exploited sex ratio strongly skewed in favour of females (Garratt et al. 1994, Mann et al. 2005). 

Commercial data show that since 2000 commercial fishing effort has declined dramatically in the South African line fishery 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 Fisheries 2012).

Threats

Chrysoblephus anglicus is vulnerable to overexploitation by line-fishing due to its relatively limited distribution (Smith and Heemstra 1986), slow growth rate and late maturity (Mann et al. 2005). In addition, there is evidence that this species is becoming increasingly targeted in KwaZulu-Natal because of serial depletion of other preferred linefish species (B. Mann pers. comm. 2009). The risk of overexploitation may be further exacerbated because it is thought to be a protogynous hermaphrodite with its reproductive capacity having been reduced by the removal of larger (male) fish, especially on the lower KwaZulu-Natal south coast. Increased targeting of this species has resulted in high fishing mortality which has led to the "collapse" of the stock as defined by the South African Linefish Managment Protocol (<25% SBPR) (Griffiths et al. 1999).

Uses and trade

In KwaZulu-Natal, Chrysoblephus anglicus is an important species in the commercial and recreational skiboat fisheries (Mann et al. 1997, Dunlop and Mann 2013) particularly on the south coat of KwaZulu-Natal (Garratt et al. 1994, Mann et al. 2005). This species is also taken by competitive spearfishers (Mann et al. 1997). Chrysoblephus anglicus contributes approximately 6% of the total commercial linefish catch in KwaZulu-Natal and a total catch of 49.7 tonnes was reported in 1992 (Garratt et al. 1994). Chrysoblephus anglicus also comprises approximately 4.7% of the total commercial catch in southern Mozambique taken by lineboats operating out of Maputo (van der Elst et al. 1994). Historic data show that while CPUE and catch composition has increased slightly, this is thought to be due to a change in targeting (Garratt et al. 1994). The sex ratio has been heavily skewed towards females due to the removal of larger male fish, especially on the lower KwaZulu-Natal south coast. Based on this information and the stock assessment undertaken by Mann et al. (2005), a precautionary approach has been taken with regard to the management of this potentially vulnerable species.

Conservation

The first conservation actions for this species were implemented in South African legislation in 1984 and included a daily bag limit of five fish per person per day (regulations in terms of the Sea Fisheries Act No. 58 of 1973). Amendments were made to this legislation in April 2005 whereby the daily bag limit for recreational fishers was reduced to two fish per person per day and a minimum size of 40 cm TL implemented for all fishers while there is no commercial bag restriction (Department of Agriculture, Forestry and Fisheries 2012). Based on spawning biomass per recruit model predictions, effective implementation of these later regulations should result in stock rebuilding (Mann et al. 2005). In addition to traditional fisheries management, a number of large no-take marine protected areas (MPAs) have been established along the South African coast and are likely to provide important protection for the resident populations of this species (B. Mann pers. obs.). One of the most recent MPAs to be established was the Pondoland MPA between Port Edward and Port St Johns and extending out to the 1,000 m depth contour (Mann et al. 2006) primarily for the protection of overexploited endemic linefish species found in the area including C. anglicus (Mann et al. 2006). The catch and effort for C. anglicus should be carefully monitored and the ongoing monitoring of MPA effectiveness for the protection of this species should also be continued (Mann and Garratt 2011).

References 

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}
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 author = {Mann, B.Q., Scott, G.M., Mann-Lang, J.M., Brouwer, S.L., Lamberth, S.J., Sauer, W.H.H. and C. Erasmus},
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,]
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