Going…going…gone?
Latest Population Assessments of Groupers
Almost half the number of grouper species (71) were re-assigned to a different category in this first reassessment of a marine SSG reflecting the importance of the decadal re-assessments recommended by the IUCN. However, in the case of groupers the change in status was rarely due to an improvement or decline in population, but rather due to improved application of the Red List categories and criteria and better understanding of the data, a change that is referred to as “nongenuine change”. This is because the Red Listing criteria have become more rigorous in the past decade requiring more quantitative evidence. Of the 71 species that changed status, 36 changed from DD illustrating new data had become available for several species. New data frequently came from independent research and surveys such as underwater visual census on coral reefs, as well as better fishery data. Many DD species were re-assigned as Least Concern (LC) and included the smaller Cephalopholis species such as C. nigripinnis and also Aetheloperca rogaa.
Two species to highlight for conservation attention in the western Indian Ocean are Epinephelus polyphekadion (Marbled grouper) and Epinephelus fuscoguttatus (Brown-marbled grouper) because their threatened status has increased. Both are now Vulnerable (VU), though were assessed in 2007 as Near Threatened (NT). The changes reflect heavy targeting of spawning aggregations, ongoing overfishing, and poor to no management across their wide Indo-Pacific range.
E. fuscoguttatus has declined on a global level by at least 30% or more since the 1970s, which covers a period of ~ two generations in length (population turnover rate x2, about 50 years), and this decline is expected to continue into the future over the next generation length (about 25 years).
The threatened grouper species are primarily large (>50cm total length) and long lived (> 20 years) and 13 species (of the 14 for which there is information) aggregate to spawn. These life history characteristics make them highly vulnerable to heavy fishing pressure.
The most common threats to groupers continue to be high and increasing fishing effort, mismanagement or no management, inadequate monitoring and poor protection through designated marine protected areas.
Epinephelus coioides, a widely distributed and large grouper is overfished in the Persian Gulf and Oman, with declines of over 50% over a period representing three generation lengths. However, it was re-assessed as LC from NT, a nongenuine change, due to better understanding of the available data, whereby good fisheries management in Australia and Indonesia places the global population status as LC. This provides a good example of the need for national efforts to improve or introduce fisheries management where this is lacking, even if global assessments suggest no cause for concern.
The Indian Ocean endemic coral grouper, Plectropomus punctatus, which is naturally uncommon in much of its range, changed from DD to LC, as a nongenuine change, due to more rigorous application of the RL criteria. Primary reasons for LC were that it is a minor component of local fisheries and there was no evidence of any decline in catches. However, with no historic fisheries data or independent monitoring data it is impossible to know how current population levels relate to unexploited or virgin population levels. Large historic declines pre 1970s can result in stable but low population levels over the last 3 generation lengths, termed the “ski jump effect” (see paper). This historic decline would not be detected by the RL criteria. Underwater visual census surveys in several WIO countries suggest Plectropomus punctatus populations are only healthy in the protected Iles Eparses in the Mozambique Channel.
Another notable change in status is that of the Giant Grouper, Epinephelus lanceolatus, which changed from VU to DD. From a conservation perspective this is of some concern as management agencies might relax any regulations around this largest of all groupers. It is the largest bony fish and the most widely distributed grouper in the world with records of a maximum weight of 400 kg, a maximum size of around 3m total length. In the WIO we have extremely limited information on this species, though found preliminary evidence of spawning aggregations which are fished in Zanzibar (see Robinson and Samoilys 2013 Book: chapter 10).
