Groupers
are a biologically diverse group of reef fishes and at least 35 different
species are harvested around the world. They
typically support small-scale, localized commercial and recreational fisheries.
The flesh is a firm, lean white meat with large flake and a mild flavor that
blends well with light seasoning or fresh herbs. Groupers are sold fresh in
local seafood markets where they are often the highest priced fish.
Catches of many groupers have declined and there is "no sign of any slowing down"
of declines (Sadovy de Mitcheson et al. 2013). In response to reduced grouper supplies, restaurants often serve some other, less expensive fish. Some restaurants have even admitted to serving basa fish (Pangasius bocourti), labeled as "grouper's cousin." It's a catfish, hardly a "cousin!" A handheld assay was developed to counter the extensive mislabeling of groupers (Ulrich et al. 2015). There is no question that fishing is the major factor driving stocks on the downward spiral, but the
several characteristics of their habitat use and life history make groupers
particularly vulnerable.
Color phases of black grouper Mycteroperca bonaci in Belize, including (A) blotched, (B) light, (C) dark, and (D) white-headed. source: Paz et al. 2007. |
Young color phase of the Giant Grouper Epinephelus lanceolatus By © Citron source |
Why
are so many groupers threatened with extinction? One fourth of all grouper species are either
near threatened or at risk of extinction if current trends continue (Sadovy de
Mitcheson et al. 2013). Many more species (33%) are data deficient, which makes assessment of fisheries status
and extinction risk impossible and management interventions unlikely (Luiz et
al. 2016). Several aspects of the life
history of groupers helps to explain the prevalence of overharvest.
Grouper Head On Photo by Craig O'Neal. Source |
First,
adult and juvenile groupers often use very different habitats and in many cases
ecosystems that support juveniles and adults are threatened from human
modification. Coral reefs throughout the
world are changing due to climate change, ocean acidification and coral
bleaching (Arundsen et al. 2003). Coral
reef fish declines directly limit the food base for adult groupers. Eggs and larval groupers are pelagic and are
transported via currents to juvenile habitats.
Juveniles often settle in different shallow water habitats. The juvenile habitats are essential to
maintain steady recruitment of new adults to the coral reefs. However, these shallow water habitats are
often degraded or transformed to less productive habitats.
Kite-shaped Epinephelus larvae. Photo courtesy National Marine Fisheries Service source |
During spawning the groupers aggregate at specific spawning locations. Here they are vulnerable to overexploitation. Especially where large aggregations exist, large grouper may be quickly reduced in abundance; the first fisherman to find the aggregations hit the bonanza and can’t reel them in fast enough. Their gears are fully saturated. It’s a phenomenon that fisheries professionals have named hyperstability (Erisman et al. 2011). Because fisherman can’t catch them fast enough, the catch per unit effort remains high even as populations plummet. In the case of the Nassau Grouper Epinephelus striatus, declines were first noticed when spawners failed to show at historical spawning aggregation sites (Coleman et al. 1996; Aguilar-Perera et al. 2014).
Hyperstable relationship between catch per unit effort (cpue) and population size (N) (Erisman et al. 2011). |
Photographs from the 'Gulf Stream' charter boat on (A) 14 April 1957, (B) 9 March 1958, and (C, D) between 1965 and 1979 Source: McClenachan 2009. |
Another
new development that particularly threatens the groupers is the live reef food fish trade (LRFFT). LRFFT involves the capture of
reef fish that are kept alive for sale and consumption as a luxury food item,
primarily in the coral triangle region. Some
small groupers are raised in cages (Pierre et al. 2008). However, this form of mariculture depends on
harvest of juvenile groupers as seed stock and the resulting fisheries are likely to be
unsustainable (To and Sadovy de Mitcheson 2009). The unfortunate reality for the groupers is
that the demand for live groupers for international trade far outstrips the
sustainable supply (Sadovy et al. 2003).
One allure of the grouper is the massive size reached by some species. The Giant Grouper (Epinephelus lanceolatus) grows
up to 2.7 m (8.9 ft) in length and 400 kg (880 lb) in weight. The larger grouper species are more likely to be threatened or critically endangered (Ruiz et al. 2016).
Atlantic Goliath Grouper Photo by Brett Seymour - source |
Largest Goliath Grouper source |
The
extreme size alone, adds to the interest and pressure by fisherman. In fact,
the sport anglers in Florida want the current harvest moratorium on Goliath Grouper lifted. Fisherman are willing to pay between $34 and $79 for a single
harvest permit (Shideler et al. 2015).
The story of the grouper is similar in all regions where they exist. Fish are quickly overharvested and fishers move from aggregation to aggregation until the grouper population is unable to recover. The efforts to recover Goliath Grouper and Nassau Grouper are longterm efforts that benefit from recent studies of population structure (Jackson et al. 2014). For more background on the Nassau Grouper efforts, view the Groupers Last Stand. The lessons from management of groupers indicates that recovery will not be quick nor easy. Length or creel limits are often ineffective if fish are released with barotrauma after deepwater capture. Successful efforts will most likely rely on community based management and adoption of principles from Ostrom's Governing the Commons, so that local knowledge is incorporated to match rules to local conditions and customs and community members monitor users and enforce the sanctions. Other local management interventions may include bans on sale of grouper during reproductive seasons, wise implementation of marine protected areas, shift to grouper tourism via SCUBA diving (Rudd and Tupper 2002), and adopting international standards for the trade in international live reef food fish. Protective management actions will take decades to evaluate because of the long time to maturity and long recovery times for groupers. Consequently, a precautionary approach to harvest management is advisable for the many data-deficient species of groupers.
References
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