ReefKeeper International has requested that the Puerto Rico Department of Natural and Environmental Resources enact regulations to prohibit fishing of a spawning aggregation of tiger grouper (Mycteroperca tigris) at the reef promontory known as El Seco, off Vieques Island. We've requested that all fishing be prohibited during the spawning season, from January to April. This action is necessary to prevent the elimination of this spawning aggregation, ensure that a sufficient number of males are present for future generations, and to help rebuild tiger grouper populations.
The Importance of Spawning Aggregations Spawning aggregations represent a large concentration of fish over a small area for the express purpose of reproduction. Many reef fish species only reproduce when aggregated during a very narrow period of time. Successful reproduction requires that a sufficient number of fish be present and allowed to reproduce. If reproduction is largely unsuccessful, the future of the stock may be jeopardized since far fewer larvae will be produced.
The Risks There is considerable evidence that unprotected spawning aggregation areas can -- and have been -- fished out of existence. Spawning stocks are targeted and particularly vulnerable to exploitation during mass spawning aggregations (Bohnsack, 1989). Spawning aggregations have shown signs of overfishing in the Virgin Islands (Olsen & LaPlace, 1978). One spawning aggregation on St. Croix has disappeared (Bohnsack, 1989). Catches from spawning aggregations in Belize declined 81% over 10 years (Carter, 1988). The Western Dry Rocks spawning aggregation off Key West has never recovered from fishing decimation (GMFMC, 1992).
The risks to spawning aggregations are compounded for stocks which are already overfished. Populations of these species are too low to maintain sustainable fisheries. Removal of adult fish at an aggregation site prior to spawning will only impede rebuilding of these populations.
The U.S. Caribbean Fishery Management Council has acknowledged these risks and recognized the need to protect spawning aggregations in federal waters off Puerto Rico and the U.S. Virgin Islands. To date, the U.S. Caribbean Fishery Management Council has closed the following areas to fishing during the spawning season:
It is quite clear that reef fish spawning aggregations can be subjected to high and unrelenting fishing pressure, that rebuilding and sustaining reef fish populations are both directly and immediately dependent on the survivability of actively spawning fish, and that therefore there is ample justification to protect mass spawning aggregations from fishing.
El Seco Tiger Grouper Spawning Aggregation The tiger grouper spawning aggregation off Vieques Island was first discovered by a local diver in the 1980s. The aggregation occurs in a 1.24 sq. km. area at a promontory of a deep reef, known locally as El Seco, 8.8 km east of Puerto Rico (approx. coordinates 18 7'6"N, 65 11'2"W) (Sadovy et al, 1994; Matos and Posada, 1998). The fish aggregate from 2-8 days after the full moon from January to April.
The El Seco tiger grouper aggregation has been the subject of scientific studies since 1993 (Padilla and Matos, 1993; Padilla and Matos, 1995; Posada, 1997; Matos and Posada, 1998; Posada, 1998). Although the average number and size of captured fish have not decreased during the study period, this spawning aggregation could easily be fished out of existence if effort increases. Fishing effort in 1998 was low due to holidays (Easter) and inclement weather. However, as fishing opportunities around Puerto Rico continue to decrease as overfishing continues, it is reasonable to expect effort on this spawning aggregation to increase.
Males Targeted Tiger groupers , like many other groupers, undergo sex reversal. Smaller individuals are female and larger individuals are male. 1998 data indicates that almost all fish caught were the more aggressive males (male/female landed 12:1). In the future, if effort increases even slightly over the 1998 levels, a substantial number of males could be removed from the population. Males in the population may decrease to dangerous levels unless efforts are made to protect the them.
Gag grouper, a relative of tiger grouper that also undergo sex reversal, have experienced exactly that problem in the Gulf of Mexico. Males have dropped from approximately 20 percent of the population to 2-10 percent of the population. The Gulf of Mexico Fishery Management Council is considering closing areas to reef fishing year round to protect spawning aggregations of gag grouper as well as protecting the males by eliminating all fishing pressure where males reside.
Overfishing No information regarding the health of the tiger grouper stock in Puerto Rico is available. Based on anecdotal reports by fishers as well as the expert opinions of many scientists, groupers and snappers are overfished in waters off Puerto Rico. Very few of these top predators are seen outside of these spawning aggregations. In the absence of a formal stock assessment, there is no reason to believe that tiger groupers are not also overfished. Protecting the El Seco tiger grouper spawning aggregation from fishing will help this species rebuild by allowing a successful breeding season to occur.
Conclusion It is quite apparent that reef fish spawning aggregations can be subjected to high and unrelenting fishing pressure. Sustaining reef fish populations and rebuilding overexploited stocks are both directly and immediately dependent on the survivability of actively spawning fish. Thus, there is ample justification to protect mass spawning aggregations from fishing. The threats to the El Seco tiger grouper spawning aggregation cannot be denied.
Therefore, ReefKeeper International has requested that the Puerto Rico Department of Natural and Environmental Resources take action to protect the El Seco tiger grouper spawning aggregation from fishing. Fishing for all reef fish should be prohibited at this location from January to April to prevent aggregating tiger grouper from being killed either by fishers targeting the species or incidentally as bycatch.
References Bohnsack, J. A. February, 1989. Protection of Grouper Spawning Aggregations. Coastal Resource Division Contribution CRD-88/89-06. NMFS-SFSC, Miami FL. Carter, J. 1988. Grouper mating ritual on a Caribbean reef. Underwater Naturalist 17: 8-11. Gulf of Mexico Fishery Management Council. August, 1992. Mutton Snapper Discussion and Proposed and Alternative Options. Tampa FL. Olsen, D.A. and J.A. LaPlace. 1978. A study of a Virgin Islands grouper fishery based on a breeding aggregation. Proc. Gulf Carib. Fish. Inst. 31: 130-144. Padilla, W. and D. Matos. 1995. Monitoring of the Tiger Grouper Mycteroperca tigris off the East Coast of Vieques, P.R. during the Aggregation of 1995. Preliminary Progress Report to the Caribbean Fisheries Management Council. Fisheries Research Laboratory, Bureau of Fisheries and Wildlife, Puerto Rico Department of Natural and Environmental Resources. August 1995. Matos, D. and J.M. Posada. 1998. Current status of the Tiger Grouper (Mycteroperca tigris) fishery at Vieques Island, Puerto Rico. Presented at 51st annual meeting of the Gulf and Caribbean Fisheries Institute, November 8-13, 1998, St. Croix, U.S. Virgin Island. Padilla, W. and D. Matos. 1993. Monitoring of the Tiger Grouper Mycteroperca tigris off the East Coast of Vieques, P.R. during April 1993. Progress Report to the Caribbean Fisheries Management Council. Fisheries Research Laboratory, Department of Natural Resources, Commonwealth of Puerto Rico. Posada, J.M. 1998. Final Report on a tag and release tiger grouper project from a spawning aggregation site at Vieques, Puerto Rico, February-March 1998. Caribbean Fishery Management Council, June 24, 1998. Posada, J.M. 1997. Final Report on a tag and release tiger grouper project from a spawning aggregation site at Vieques, Puerto Rico, February-March 1997. Caribbean Fishery Management Council, May 5, 1997. Sadovy, Y., P.L. Colin, and M.L. Domeier. 1994. Aggregation and spawning in the tiger grouper Mycteroperca tigris. Copeia. 1994(2):511-516.