The Humphead wrasse is naturally (biologically) vulnerable to fishing due to its characteristics of long life and late sexual maturation (sexual maturation occurs at approximately 35-50 cm total length and up to 5 years of age, or more). These characteristics mean that its life history is one that likely involves slow replacement (and hence slow recovery from fishing) rates.
Ten Good Reasons to Protect and Manage the Humphead Wrasse
The Humphead wrasse spawns in aggregations that can easily be targetted by fishers and hence are particularly vulnerable to overfishing at the times and places at which reproduction occurs. It has been well-documented that spawning aggregations in several other reef fish species are particularly vulnerable to being overfished.
The Humphead wrasse can change sex from female to male. This makes the species susceptible to size-selective (=sex selective) fishing that could lead to imbalances in the reproductive sex ratio and reduce reproductive potential.
Adult Humphead wrasse are very vulnerable to night-fishing, especially if SCUBA is used, since they are easily taken from the caves in which they sleep. Adults do not appear to be particularly common anywhere in their geographic range (compared to commercially taken fish in general) so that heavy nighttime fishing can quickly reduce population numbers.
The species has a high economic value and is a special favourite of both the live reef food fish trade and with recreational divers. Because of its high value as food, it is heavily sought by fishers and traders; as part of the luxury food fish market, its value is likely to increase with rarity, so fishers will continue to fish this species even as its numbers decline. On the other hand, its value to diving tourism will remain high if animals are protected and remain alive in the wild.
The most preferred trade, or market, size for this fish in the export trade as food is 'plate-sized' – between about 30-60 cm (mainly 30-45 cm) total length. Plate-sized fish are typically sexually immature since sexual maturity occurs at about 50 cm. This means that large numbers of sexually immature fish are removed from the wild for the live reef food fish trade. The relatively large sizes of these juvenile fish mean that they would very likely survive to reproduce in the wild, if not removed. If young fish are being removed before they can produce the next generation, how can populations replace themselves and recover from fishing?
There is a heavy catch of juveniles from the wild, not only for direct sale as plate-sized fish (see SIX above) but also for so-called (and misnamed) 'mariculture' grow-out in which these young wild fish are put into cages and grown-out until they attain saleable size. This juvenile capture fishery is a type of activity that most properly managed fisheries seek hard to avoid because of the negative effects on the potential for future population recovery. Juveniles need to be protected until they grow big enough to reproduce and replenish the population. In Indonesia many of these small fish are exported illegally.
Full-cycle mariculture (i.e. hatchery-based mariculture) is not yet possible for this species at commerical levels and all fish are taken from the wild. Claims of full-cycle culture have all been shown to involve the grow-out of young fish taken from the wild. While some experimental work has produced larvae, the prospect of commercial scale culture to supply the food market is still remote, possibly needing 5 - 10 more years and lots of fundings.
Cyanide is widely used to catch this species, especially in parts of Indonesia and the Philippines, and particularly for the juvenile (less than 50 cm) fish. Cyanide is often introduced by the traders of live reef fish to fishing communities that do not traditionally use this destructive fishing method. Cyanide is a poison and is known to kill living coral. The Humphead wrasse, as with many other reef fish and invertebrate species, depend on healthy coral reefs for shelter. Loss of this habitat could severely affect reef communities, and their habitats.
Humphead wrasse fisheries are typically unmanaged and, even if managed 'on paper', there is usually little management or monitoring of Humphead wrasse in local fisheries. Monitoring is urgently needed, both of local capture and of exports. Without proper management and monitoring, it is impossible to know whether current capture rates are sustainable or to establish safe quotas for the capture of this vulnerable species.