On the 22nd February 2023 the ORI Cooperative Fish Tagging Project (ORI-CFTP) had its 343rd Black musselcracker/Poenskop tag recapture.
This musselcracker was originally tagged on the 29th June 2018 by Robert Gordon Kyle in the surf near the Duiwenhoeks River in the Western Cape (WC), measuring 50 cm fork length (FL). It was recaptured 1 699 days (4.7 years) later by Richard Hartwell in the Wilderness area, WC, measuring 56 cm FL. This fish only grew 6 cm during its time at liberty and moved about 190 km up the coast.
Black musselcracker are an endemic species found from Cape Agulhas in the WC, to Ponto do Ouro in southern Mozambique. Adults are found on high-profile inshore and offshore reefs down to depths of at least 100 m, while juveniles are found in the rocky surf-zone and on shallow subtidal reefs. Juveniles are highly resident in the Eastern and Western Cape. Some adults undertake a uni-directional movement up the east coast to Transkei and KwaZulu-Natal waters, presumably to spawn. This recapture may be an example of this type of movement. Females mature at about 53 cm FL and an age of about 10 years. This fish has an extremely slow growth rate and changes sex from female to male (protogynous hermaphrodite) at about 70 cm or 18 years of age, with all fish greater than 95 cm FL being males. They can reach a maximum size of 110 cm FL, a weight of up to 37.8 kg and a remarkable age of 45 years.
Although the black musselcracker stock has not been assessed, it is estimated that this species has declined to approximately 20% of its historical abundance. They have been evaluated as Vulnerable on the IUCN Red List and have a Red (DO NOT BUY) status on the SASSI list. Slow growth, late maturity and sex change make the black musselcracker extremely vulnerable to over-exploitation. Strict regulations are therefore in place to help protect this species, including a minimum size limit of 50 cm total length and a daily bag limit of one fish per person per day. Marine Protected Areas (MPAs) with suitable reef habitat are extremely important for the conservation of this vulnerable species throughout its distribution.