|Scientific Name:||Mycteroperca microlepis|
|Species Authority:||(Goode & Bean, 1879)|
Trisotropis microlepis Goode & Bean, 1879
|Red List Category & Criteria:||Least Concern ver 3.1|
|Assessor(s):||Bertoncini, A.A., Choat, J.H., Craig, M.T., Ferreira, B.P. & Rocha, L.|
|Reviewer(s):||Sadovy, Y. & Moss, K. (Grouper and Wrasse Red List Authority)|
Mycteroperca microlepis is listed as Least Concern because it is a widespread and abundant species. There has been local decline due to overfishing in the Gulf of Mexico, but this species is not currently threatened overall. Several conservation measures are in place targeted to this species. A regional assessment may be warranted for the US.
|Previously published Red List assessments:||
|Range Description:||Mycteroperca microlepis is a western Atlantic species with a wide, disjunct distribution from North Carolina (USA) (with juveniles occurring as far north as Massachusetts) to the Yucatan Peninsula, Mexico and southern Brazil. Gag are rare in Bermuda and there is one record in Cuba; otherwise the species is not known from the Caribbean or northeastern Brazil.|
Native:Bahamas; Bermuda; Brazil; Mexico; United States
|FAO Marine Fishing Areas:||
Atlantic – western central; Atlantic – northwest; Atlantic – southwest
|Lower depth limit (metres):||167|
|Upper depth limit (metres):||33|
|Range Map:||Click here to open the map viewer and explore range.|
Mycteroperca microlepis is a common species found in soft bottom and rocky ledges in the Gulf of Mexico and southeastern and south Brazil. Although heavily fished and presume to be overfished, the current trend and catch data is unclear.
Fishery-independent data by country
Based on the information from Reef Environmental Education Foundation (REEF), the sighting frequency (SF; a value calculated as dividing the number of survey with gag encountered [n] by the total number of survey carried out in a particular year [N]) of gag in tropical western Atlantic stayed low at <3% from 1993 to 2005, with a mean value of 1.4% (www.reef.org/data; accessed on 2nd Feb 06).
See the supplementary material for Table 1: sighting frequency of M. microlepis in tropical western Atlantic.
According to interviews with grouper fishers in the early 1990s, the northwest Florida grouper fishers reported that there was a steady decline in the landings of gag over the past decades [all Gulf groupers were lumped in the landings data before 1986] (Koenig et al. 1996).
Based on 64 dives from 1977 to 1982 by manned submersibles on the east of Florida continental shelf, none of gag sized <70 cm SL (Gilmore and Jones 1992).
According to manned submersible videotape observations done on the east coast of Florida, the percentage composition of gag of all reef fish on Jeff’s Reef decreased from 4.774% in 1980 (n=4,375) to 0.07% in 1995 (n=1,399) (Koenig et al. 2000).
South Carolina, USA
Based on four hours of a flood tide and sampling on the top 2 m of the water column, the total number of postlarval gag entering Price Inlet, South Carolina, over a 10-week period in 1983 and 1984 was estimated to be 365,400 and 904,050, respectively (Keener et al. 1988).
North Carolina, USA
During a 200-hour hook-and-line fishing 20 to 60 miles offshore in water 12.2 to 42.1 m deep off Onslow Bay, North Carolina, from May to August 2003, 593 groupers were caught (total catch = 1,249) in which gag accounted for 9.3% (n=55) of the grouper catch (Bacheler and Buckel 2004).
From May 1996 to September 1997, M. microlepis comprised 6% in weight and 2% in number of all grouper catches (17 species) from technified boasts on Campeche bank, southeastern Gulf of Mexico (Colas Marrufo et al. 1998).
During a 19-month survey at the northern coast of Yucantan in 2000 to 2001, 928 specimens of M. microlepis were caught by a small trawl net and all of the fish were found to be sexually immature juveniles (Renin et al. 2004).
Available data on the landings of M. microlepis quoted from different studies and sources show that the quantity of commercial and recreational catches of gag increased steadily from 1980 to 2004, with recreational catches comprised with an average of 55% in 1995 to 2004. As a result, both commercial and recreational fisheries have significant impacts on the stock of this grouper species.
Stock assessment (1994) by Schirripa and Goodyear
Based on virtual population estimates (VPA) tuned to the percent frequency of age three in recreational catch and natural mortality = 0.20, Schirripa and Goodyear (1994) estimated the abundance of M. microlepis in US Gulf of Mexico ranged from 5.7 million to 9.3 million fish in 1986 to 992.
See the supplementary material for Table 2: stock at age at beginning of year in US Gulf of Mexico.
Of the seven Virtual Population Analysis models examined, no single model stood out as the best overall view of the stock (Schirripa and Legault 1997). Integrated Populations Analysis was employed to modeling the gag stock. The results suggested that the recruitment of M. microlepis was highly variable and the very young fish suffer little fishing mortality. However, older fish faced increasing fishing pressure with age such that very few fish survive longer than 10 years.
See the supplementary material for Table 3: calculated commercial landings (gutted weight) of M. microlepis from the US waters in the Gulf of Mexico from 1986 to 1992.
On the basis of the uncertainty associated with the sensitivity of the reproductive strategy of M. microlepis to overfishing, Schirripa and Legault (1997) felt that Spawning Potential Ratio (SPR) should be maintained well above the 20% minimum adopted by the Gulf Council in its definition of overfishing.
See the supplementary material for Table 4: estimated population size from VPA using the IPA method.
Turner et al. provided catch statistics for gag from 1986 to 2000.
See the supplementary material for Table 5: calculated commercial landings (gutted weight) of M. microlepis from the US waters in the Gulf of Mexico from 1986 to 2000.
The total catch (landings and discards, in terms of number of fish and metric tonnes) of gag in the Gulf of Mexico by sector for 1986 to 1999 are shown in Table 6 (Turner et al. 2001).
See the supplementary material for Table 6: total catch (landings and discards, in terms of number of fish and metric tonnes) of M. microlepis in the Gulf of Mexico by sector for 1986 to 1999.
Four sets of VPA runs (two catches-at-age by two selectively assumptions) and one set of additional runs contrasted the effects of the different growth curves sued in this assessment about index selectivity, two sensitivity runs were made (recruitment and commercial indices, and recruitment and recreational indices. Modeling results indicated that the catch-at-age used for 2 sets of analyses differed. The recruitment-and-mortality-modulated catches-at-age showed that larger catches of age 0 and lower catches of age 1 to 4 and 5 to 9. The estimated fishing-mortality rates in 1999 from the RMM catches-at-age were higher on age two and lower for age four. In the year-constant selectivity analyses, the selectivity patterns differed between the two catches-at-age. By an large, a wide range of fishing-mortality rates and associated abundances were estimated, concluding that there was uncertainty in the gag stock in 1999 in the Gulf of Mexico. And some of the estimates might be unrealistic based on what might be considered very large changes in abundance.
It was suggested that if the recruitment-and-mortality modulated (RMM) ageing approach is to be used in the future, consideration should be given to incorporating the ageing and assessment phases in the same routine so that a simultaneous solution for all parameters could be obtained in a statistical modeling approach. Recommendations on the use of statistical estimation systems should consider error assumption in catches and other inputs.
Fishery-dependent data by country
Historically, gag in Florida had often been confused with black grouper (M. bonaci), and commercially caught M. microlepis were also included in the “unclassified grouper” statistics before 1986 (GMFMC 2001).
In 1987 to 1997, M. microlepis accounted for an average of 19% (15 to 23%) of the total classified grouper landings (Schirripa 2000).
In 1973, gag from offshore water (>40 m depth) off North Carolina and South Carolina were almost always greater than 800 mm TL (the saturated large adult might prevent recruitment by social exclusion or by intraspecific predation). After 15-year intensive fishing, almost no individuals exceeding 800 mm TL could be taken from headboats in the Cape Lookout (Huntsman et al. 1999).
When compared with sex-size data collected before the 1980s, sex-size-frequency data from gag collection in 1991 to 1993 indicated several changes in population structure: reductions in the average size of females and males, and the proportion of males (from about 17% to <2%) (Koenig et al. 1996). Koenig et al. (1996) also suggested that fishing selection for males during the spawning seasons is highly responsible for the above changes in the population of gag.
Gag accounted for over 80% of the total commercial landings by weight of Mycteroperca species in 1985 in offshore waters of Carolinas (Keener et al. 1988).
According to the annual commercial fishery landings of the NMFS, the quantity of gag caught in the USA increased steadily from 55.8 mt to 1,616.4 mt in 25 years (Table 7) (www.st.nmfs.gov, accessed on 2nd Feb 2006).
See the supplementary material for Table 7: annual commercial fishery landings (NMFS) of M. microlepis caught in the USA.
In the Gulf of Mexico, the estimated annual commercial landings were about 0.7 metric tonnes from 1986 to 1992, with size and age ranged from 9 to 55 inch TL, and 0 to 20 years (Schirripa and Goodyear 1994).
It was observed that GAG was a large part of the domestic catch of Gulf of Mexico grouper fishermen west of Florida, comprising almost all of the US Gulf of Mexico harvest of this species was from Florida (Schirripa and Goodyear
Schirripa and Goodyear (1994) estimated the harvest of GAG by recreational fishers from 1979 to 1992 ranged from 0.2 million fish in 1979 to 0.8 million fish in 1985, with size and age ranged from 8 to 58 inch TL, and 0 to 18 years. Stricter regulations enacted in 1990 reduced harvest to about 0.24 million fish (Schirripa and Goodyear 1994) (Table 8).
See the supplementary material for Table 8: the recreational harvest estimates for Gulf of Mexico gag in 1979 to 1990.
According to the NMFS, the annual recreational harvest estimates of both number and weight of M. microlepis increased steadily during the period between 1981 to 2004 (despite of the substantial increase in weight in 1984 [with proportional standard errors (PSE) of 53, which is associated with the annual estimates of landings by number]) (http://www.st.nmfs.gov/st1/recreational/queries/catch/time_series.html; accessed on 2nd Feb 2006) (Table 9).
See the supplementary material for Table 9: The annual recreational harvest estimates of both number and weight of M. microlepis between 1981 and 2004.
According to NMFS’s statistics on commercial and recreational fisheries landings, an average of 53% of the total landings were caught by recreational fisheries in 1987 to 2004 (Table 10).
See the supplementary material for Table 10: commercial and recreational fisheries landings (1987 to 2004).
In April and July 1996, 27.8% (n=155) of all GAG (N=559) caught by commercial hook-and-line fishery off northwest Florida was considered to be bycatch - undersized (< 508 mm TL) or those discarded by fishers as undersize fish. Although the legal minimum size limit was 508 mm TL, some undersized fish (9.9% of all GAG) was landed as legal. In addition, all undersized GAG were found to be immature female (Johnson et al. 1997). However, in another study (Bacheler and Buckel 2004), the sublegal grouper caught only accounted for a small percentage of the overall grouper catch (6.8%), and the proportion of sublegal caught per day decrease with depth.
From 1980 to 1999, 15,400 metric tonnes were landed in the southeastern U.S.. Landings per year increased over the period, but effort data are lacking. During this time, gag composed approximately 33 % of commercial landings of grouper, and 15 % of commercial reef fish landings in the Gulf of Mexico.
In 1985, in off-shore waters of the Carolinas (US), gag accounted for over 80 % of total commercial landings for Mycteroperca species.
The US National Marine Fisheries Service classified gag as approaching a condition of overfishing in 1998. As a result, several actions including increasing the minimum size limit and a periodic closure during the spawning season from 15 February to 15 March was instituted and some marine protected areas were developed that included gag.
The status of the Campeche Bank gag stock remains largely unknown. Data on biology, landings, catch per unit effort, catch composition, and size trends for gag from Mexican waters are not available.
The Gulf of Mexico stock is currently classified as overfished, but the south Atlantic stock appears is in relatively good shape (NOAA Fish Stock Sustainability Index 2006).
|Current Population Trend:||Decreasing|
|Habitat and Ecology:||
Mycteroperca microlepis is a reef-associated species usually found offshore on rocky bottom (rarely to 152 m), and occasionally inshore on rocky or grassy bottom. Juveniles occasionally occur in estuaries and seagrass beds. It is the most common grouper on rocky ledges in the eastern Gulf of Mexico. Adults are either solitary or in groups of 5 to 50 individuals. Gag appears to prefer habitats characterized by maximum structural complexity, such as living Oculina coral reefs, at depths between 70 and 100 m (McGovern et al. 1998). In southern Gulf of Mexico, juvenile females were caught inshore at depths of 1 to 10 m, and adult females and males, and transitionals were caught offshore at depths of 33 to 167 m (Brule et al. 2003).
Gag usually feed on fishes, some crabs, shrimps, and cephalopods. Juveniles (less than 20 cm) feed mainly on crustaceans that live in shallow grass beds. The principal prey items of estuarine gag included calanoid copepods, mysids, gammaridean amphipods, grass shrimp, penaeid shrimp, and fishes (Mullaney 1993).
Reproduction, maturity and growth
Gag are protogynous hermaphrodites, and females have been shown to outnumbered males 6:1 or greater in heavily fished areas. Females mature between ages III and VI, and no males less than age V were observed. Analyses of gonad condition suggested that gag spawn from December to May, with peak activity occurring during February and March (Hood and Schlieder 1992).
Maximum age assumed as 17 years by Hood and Schlieder (1992) and 20 years by Collings et al. (1987).
In the Gulf of Mexico, females reach first maturity at 72.1 cm (FL) (Brulé et al. 2003) and spawns at depths of 50 to 53 m from early winter to mid-spring (January and March).
Gag have suffered a drop in the proportion of males from 17 to 1% in the last 20 years (Coleman et al. 1996), and McGovern et al. (1998) reported a decrease from 19.6% (1976 to 1982) to 5.5% (1994 to 1995), and also suggests a decrease in the size at first maturity.
51% of females at age IV had mature ovaries. Transitional males ranged in age from V to XI yrs (750 to 950 mm TL) (Collings et al. 1997). A dramatic change in age-size structure of gag population over 11 years (79 to 80 to 1991) and in 1991 minimum size adopted was 51 mm (TL).
Gag forms spawning aggregations in deep reefs built by Oculina coral. The fisheries targeted greater depth, that lead to dramatic change in sex ratio (15:1 female:male).
Collins et al. (1997) stated gag was a multiple and indetermine spawner.
Reproductive season begins in November or December and last till May or June (Turner et al. 2001).
In the South Atlantic Bight, gag spawned once a year in late winter to early spring, with peak spawning activity occurring in late March and early April (Collins et al. 1987). Spawning aggregations were concentrated at depths of about 80 m (ranged from 50 m to 120 m) (Koenig et al. 1996). Gag were in spawning condition from December to mid-May in southern Florida, January to May in northern Florida, and January to April in South Carolina, with peak spawning activity occurred from March to mid-April in all areas (McGovern et al. 1998). In southern Gulf of Mexico, gag spawns at depths of 50 to 53 m, from early winter to mid-spring, with peak spawning activity occurring between January and March (Brule et al. 2003).
M. microlepis were found to form large spawning aggregations at depths ranging from 50 to 120 m (Schirripa and Goodyear 1994). Gag was documented to form spawning aggregations in the greater Caribbean region (Luckhurst 2003). Coleman et al. (1996) indicated that the status of spawning aggregation in the Gulf Coast was declining. At least one spawning site in the eastern Gulf of Mexico had been reported, where gag were observed to be attracted to high-relief sites for spawning aggregation (Koenig et al. 1993).
M. microplepis is a monandric (Brule et al. 2003), protogynous hermaphrodite (McErlean and Smith 1964). Females become sexually mature at five or six years (67 to 75 cm TL) and most change sex to male between 10 and 11 years old (95 to 100 cm TL) (Heemstra and Randall 1993).
In the south Atlantic Bight, the smallest mature female was 600 mm TL, with 28% of age 3 female had mature gonads. In southern Gulf of Mexico, 50% of female (n=161) reached first maturity at 72.1 cm FL (Brule et al. 2003).
In eastern Gulf of Mexico, the smallest mature female was 400 mm SL, and all females of size >550 mm SL were mature (Koenig et al. 1996). Also in eastern Gulf of Mexico, Hood and Schlieder (1992) found that female matured as early as age two, >70% were mature by age four, and all were mature by age six.
Size range for fish undergoing sex succession was 750 to 950 mm TL, with five transitionals aged five, six, seven, eight and nine years (Collins et al. 1997). In eastern Gulf of Mexico, size ranges of transitionals were reviewed to be 525 to 1,175 mm TL (Koenig et al. 1996). In eastern Gulf of Mexico, 50% of sampled females had changed into males at 103 cm FL; sexual transition seemed to occur at 85 to 111 cm FL (Brule et al. 2003).
Based on 12 out of 1,331 specimens, Hood and Schlieder (1992) found that gonads of age 5 to 13 gag (n=12, five of them were aged eight or nine years) were transforming into testes.
Sex change occurs near the time of spawning aggregation formation (Koenig et al. 2000).
McGovern et al. (1998) revealed that female gag might have been maturing at smaller sizes during 1994 to 1995 than during 1976, because this stock was stressed.
Recruitment and fecundity
Based on four hours of a flood tide and sampling on the top 2 m of the water column, the total number of postlarval gag entering Price Inlet, South Carolina, over a 10-week period in 1983 and 1984 was estimated to be 365,400 and 904,050, respectively (Keener et al, 1988).
Fecundity of a 95 cm female was estimated at 1.5 million eggs (Heemstra and Randall 1993). A single M. microlepis at age eight produces as many eggs as 48 M. microlepis at age three (Collins et al. 1998). McErlean (1963) estimated the fecundity to be 655,000 to 1,457,000 eggs.
Sea surface temperatures affected by the Gulf Stream response to the Charleston Bump (a deep, rocky, bottom feature located on the Blake Plateau southeast of Charleston, South Carolina, USA) appeared to play a determining role in recruitment success in gag (Sedberry et al. 2001).
Mycteroperca microlepis is intensively fished by commercial fishermen, sport divers, and anglers particularly at the spawning aggregations.
Other threats include low productivity (Ault et al. 1998), protogyny, spawning aggregation formation, vulnerable to overfishing (Huntsman et al. 1999), and destruction or modification of the nursery areas (Renin et al. 2004).
Owing to the very narrow nature of the continental shelf, spawning aggregations are easily accessed and gag off Florida are subject to intense fishing pressure, particularly during late fall through early spring (McGovern et al. 1998).
Juveniles are often caught as a part of by-catch of the bait-shrimp fishery in grass bed habitat (Schirripa and Goodyear 1994). From April to July 1996, 155 immature females (representing 75% of all grouper bycatch and 27.8% of all 559 gag) were caught as bycatch from commercial hook-and-line fishery off northwest Florida (Johnson et al. 2004).
Although the commercial fishery catches larger fish (on an average) than does the recreational fishery, the recreational fishery accounted for about 78% of the total number of gag caught (Schirripa and Goodyear 1994). Schirripa and Goodyear (1994) also suggested that the 20 inch minimum size regulation put on in 1990 had resulted in a marked increase in the numbers of gag subjected to the very uncertain discard mortality rate (Schirripa and Legault 1997).
Schirripa and Legault (1997) suggested that commercial discards were smaller than those from the recreational fishery due to less targeting in conditions where smaller sized fish were vulnerable.
Fitzhugh et al (2003) found that the youngest ages (three and four years) were taken in the recreational sector, followed by commercial hook-and-line (age five and six years) and finally commercial long-line sectors. Fitzhugh et al. (2003) also supported earlier studies showing larger and older fish tend to be sampled from deeper water depths.
Fitzhugh et al. (2003) suggested that recruitment variation changes the adult age-structure.
The increase in the estimated total number of M. microlepis caught and released indicated that the regulation had some restrictive effect on the number of fish being kept illegally (Schirripa and Goodyear 1994).
Overfishing of adults and juveniles as well as the destruction or modification of their nursery had lead the M. microlepis to be regarded as a vulnerable species (Renin et al. 2004).
The dramatic decrease in the percentage of male in spawning aggregations (17% to 1% in 20 years) had caused concerns about sperm limitation, disruption of sex change processes, and excessive inbreeding (Koenig et al. 2000, Chapman et al. 1999, Coleman et al. 1996).
If spawning sites are traditional and the aggregation sites in northern Gulf of Mexico have been depleted by fishing, it is likely that continued aggregation fishing would eliminate other aggregations sites (Koenig et al. 1996).
Chapman et al. (1999) commented the size-limited population of M. microlepis suffered from restricted gene flow among genetically differentiated population, reflecting the offsprings would be more likely to be genetically related due to inbreeding.
Fishing mortality of age five fish was estimated to be F (fishing) =0.21 for M (natural) =0.20, and F=0.25 for M=0.15 (Schirripa and Goodyear 1994).
The grouper fishery is managed by the South Atlantic Fishery Management Council under the Snapper-Grouper Fishery Management Plan. Current regulations include a limited entry fishery where a limited number of commercial fishing permits are available, a seasonal closure during March and April to reduce the commercial catch and minimum size limits. These regulations have helped stocks to recover; the most recent stock assessments show that gag is not overfished or undergoing overfishing in the south Atlantic, but it is overfished in the Gulf of Mexico. Regulations are under consideration that would establish a Total Allowable Catch (TAC) for the commercial grouper fishery in the southeast. A TAC will greatly enhance the sustainability of the grouper populations.
There are closed areas in the Gulf of Mexico (Madison-Swanson) and South Atlantic (Oculina HAPC) where spawning of gag probably occurs. In addition, US Amendment 14 to the Snapper Grouper Fishery Management Plan of the South Atlantic Region will be implemented during 2007. This amendment implement protection to Oculina Banks which harbour spawning aggregation of this species. Spawning gag have been collected from several of the proposed South Atlantic MPAs.
M. microlepis was included on the Red List of the IUCN in 1996.
Classified as vulnerable by U.S. Fish and Wildlife Service (USFWS)’s concept of District Population Segments (DPS) (Musick et al. 2000).
In 1985, a minimum size limit of 18 inches was enforced in Florida. In 1990, the Gulf of Mexico Fishery Management Council adopted a 20-inch minimum size, five-fish aggregate grouper bag limit for recreational fishers, and a commercial shallow-water quota of 9.8 million pounds in the Exclusive Economic Zone (Schirripa and Goodyear 1994). On 19th June 2000, commercial and recreational minimum size limits were increased to 24 and 22 inch TL. At the same time, sales of gag were prohibited 15th February to 15th March, and two marine reserves in which fishing for reef fish and bottom oriented species was prohibited year round were established (Turner et al. 2001; http://www.gulfcouncil.org/oldstories/2002-03-26-Gag%20Status%20Change%20Requested.htm; accessed on 15th Feb 2006).
Based on the 1992-1994 catch curve and the assumption of constant fishing effort, the minimum size limits reduced projected landings in numbers to 86.5% of historical levels for 18 inch TL, 70.9% for 20 inch, and 43.4% for 24 inch TL. Projected declines in landings weights were 96.8&, 90.7% and 73.7%, respectively (Bohnsack 2000).
Based on the results of the 2001 gag stock assessment and the October 2001 report of the Council's Reef Fish Stock Assessment Panel (RFSAP), the Gulf of Mexico Fishery Management Council (GMFMC) had requested since 26th March 2002 that NMFS reclassify the status of the gag stock in the Gulf of Mexico region from "undergoing overfishing" and "not overfished but approaching an overfished condition"; to "not undergoing overfishing" and "not overfished". GMFMC suggested that the stock of gag appeared to meet this classification even under the more conservative guidelines for determining overfished and overfishing status that resulted from the Sustainable Fisheries Act of 1996 (SFA) (Tables 11 and 12). In the NMFS annual Report to Congress on the Status of Fisheries of the United States, this would change the status of gag as follows (http://www.gulfcouncil.org/oldstories/2002-03-26-Gag%20Status%20Change%20Requested.htm; accessed on 15th Feb 2006).
See the supplementary material for Table 11: current status of M. microlepis; and Table 12: requested change in status.
GMFMC (2001) indicated that a substantial number of undersized M. microlepis was released, some potential regulatory measures might have les effectiveness on actually reducing mortality than would be preferred, due to release mortality. As a result, continued research on the caused of release mortality was recommended.
Goodyear (1996) indicated that large minimum sizes may cause the fishery to harvest the faster-growing component of each year class, thus could induce genetic selection for slow growth, depending on the heritability of growth. Such selection may lead the fish subject to high release mortality. On the other hand, Johnson et al. (1997) suggested that small size limit would result in killing large fractions of the population before they spawn.
Bacheler and Buckel (2004) found that circle hooks significantly reduced gut hooking, and also suggested a trade between fishing in shallow water to reduce depth-related injuries to grouper and fishing in deeper water to minimize the catch of sublegal grouper.
Boyan (2000 in press) indicated that less than 2% of reported commercial catches occurred in the closed, fishery-protected area, and there was not enough enforcement to keep boast from illegal fishing. Moreover, Boyan (2000 in press) further pointed out one-month closure failed to largely reduce commercial landings because spawning aggregation lasts for three months. In addition, increased 24 inch size limit only reduced 30-36% and 16% of the recreational and commercial takes, respectively.
Gilmore and Jones (1992) suggested that a closed season would be more likely to protect spawning stocks than size limitations. They also pointed out that the upper size limitations on grouper fisheries may be more effective in shallower waters.
Koenig et al. (2000) emphasized that shelf-edge fishery reserves are necessary to manage the gag fishery and to ensure optimum reproductive capacity.
|Citation:||Bertoncini, A.A., Choat, J.H., Craig, M.T., Ferreira, B.P. & Rocha, L. 2008. Mycteroperca microlepis. The IUCN Red List of Threatened Species 2008: e.T14050A4386366. . Downloaded on 10 February 2016.|
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