Going, going…, gone? – latest population assessments of groupers



Groupers are among the highest valued fish in fisheries globally, are crucial for food security in developing countries, and in coral reef ecosystems play a key ecological role as top-level predators.Their population status around the world was reassessed after a decade by the IUCN Grouper and Wrasse Species Specialist Group (SSG) (https://www.iucn.org/ssc-groups/fishes/grouper-and-wrasse) of which Melita Samoilys is a member. The latest assessments were published by IUCN in November 2018 and the key findings have just been published in Marine Policy. The results show clearly that earlier warnings of the vulnerability and plight of groupers worldwide published by the SSG in 2013 (see Sadovy de Mitcheson et al 2013): appear to have had little effect on the population status of this important family of fishes. Their status has not improved: 19 species out of all 167 species of grouper were assessed as threatened: Vulnerable (VU), Endangered (EN), or Critically Endangered (CR) (see IUCN’s 2016 Red Listing Guidelines manual). A further 15% of species were assessed as Data Deficient (DD) because data are still insufficient for population assessments. Thus, overall, the proportion of groupers that are threatened is around 13% (ranging from 11% to 26% depending on whether DD species are included), and the threats are not diminishing.

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, mis-management 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.

Other important species to note whose status has improved is the Indo-Pacific, relatively common and large, Plectropomus laevis (Saddle-back coralgrouper) which has changed from VU to LC, and the smaller, naturally uncommon Roving coralgrouper Plectropomus pessuliferus, which changed from NT to LC. Both are considered nongenuine changes and are simply due to improved application of the RL criteria and interpretation of data. Overfishing is not considered to be a major threat on a global level for either species, but declines are known locally, in for example the Maldives for P. pessuliferus, due to targeting of spawning aggregations of P. laevis in the Pacific, and data deficiency for both species in the Indian Ocean is a concern.

The Indian Ocean endemic coralgrouper, 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 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).

Cephalopholis nigripinnis

Epinephelus polyphekadion, abundant in the Chagos Archipelago (see Samoilys et al. 2018) but rarely seen in the WIO (see Samoilys et al. 2019).

Epinephelus fuscoguttatus, known to form spawning aggregations in Kenya and Seychelles

Epinephelus coioides for sale in a fish market in Dubai.

Plectropomus laevis (top) and Plectropomus pessuliferus (bottom) in the Chagos Archipelago

Epinephelus lanceolatus

Despite attempts to highlight the importance of research and management of spawning aggregations in groupers and other reef fishes in eastern Africa through a MASMA funded project which ended in 2012 (Robinson & Samoilys 2013), further research and efforts to protect and manage spawning aggregations in eastern Africa have been negligible, except in Seychelles. Overexploitation in all types of fisheries remains the major threats to groupers worldwide. With few exceptions, species identified as threatened a decade ago are not better managed today. Monitoring is particularly ineffective. If it occurs, groupers are often all lumped together, or even more broadly as “demersal fishes”.
There are few examples of localised species recovery, the most notable being the Critically Endangered Nassau grouper, Epinephelus striatus, where research, strong political will and enforcement has led to recovery of spawning aggregations in the Cayman Islands; though inadequate to change its global CR threat status. Similar recovery of spawning aggregations through full protection of aggregation sites in Papua New Guinea is also reported for the VU Epinephelus polyphekadion (Marbled or camouflage grouper) and Epinephelus fuscoguttatus (Brown-marbled grouper).

It is time for governments to recognise the multi-million dollar value of grouper fisheries and their food benefits, as well as the ecosystem role these species play. This recognition will lead to better monitoring and management. In the WIO we have an opportunity to identify flagship groupers for targeted research and monitoring and so inform management to restore populations to their former healthy state. I would suggest we start with any of the Epinephelus and Plectropomus species illustrated above.

 

Find below links to full HTML Versions of the key articles:

  • Valuable but vulnerable: Over-fishing and under-management continue to threaten groupers so what now?
  • Fishing groupers towards extinction: a global assessment of threats and extinction risks in a billion-dollar fishery
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    By Melita Samoilys