C. Conservation of Spawning Aggregations

Does Protection of Aggregations Help?

In a number of places, various types of protection have been put in place to conserve aggregations. Do they help and what means can be utilized to show that they help? While it is not within the scope of the present manual to cover these protections in detail, we would like to comment on the types of protection put into place in some areas. Protection can include a prohibition of fishing in a given site, usually the aggregation area and nearby reefs, and protection of species by closed seasons during the spawning period. A combination of both types of restrictions seems most likely to have a positive effect and has been implemented in several places. The former seems the most obvious when fish(es) at certain sites are rapidly being wiped out. Closed seasons are particularly relevant where aggregations can not be patrolled or site protection readily enforced. The latter type of regulation covers aggregations that are unknown to anyone, except perhaps a few fishermen, but may have great importance in reproductive success.

Various methods can be used to prevent overexploitation of aggregations. Johannes and Kile (2001) recommended banning the catching and holding of live groupers (for the live reef fish trade) during the months of spawning aggregations, instead of trying to protect the aggregation sites which are widely dispersed and far from settlements. The type of protection implemented depends on the local social and cultural contexts as well as species and fishery conditions involved (Domeier et al, 2002). Presently the most widely applied approaches to protecting aggregating fishes are seasonal (no fishing and/or no commercial sale of the species during the spawning season) or spatial (the spawning site itself is protected during the aggregation period or is incorporated into a marine protected area).

Figure 59. These fishermen in the Cayman Islands have made a good catch of Nassau groupers from the spawning aggregation, but how long will this last. This photo was taken in 1977, a time of no regulation of the spawning site and declining catches. In earlier years, many more fish were caught, but those days were already gone. At present the fishery is closely regulated, but catches have yet to improve.

There are some signs that protection can result in increased fish size when nonaggregated populations are still fished. Beets and Friedlander (1999) documented a case where declining catch and size, plus a highly skewed sex ratio (in favor of females) among red hind, E. guttatus, in the U.S. Virgin Islands reversed after protection was put in place. They reported an increase from 295 mm SL to 395 mm SL for red hind after seven years of spawning site closure to fishing, while the sex ratio change from 1:15 males to females to 1:4.

The protection of aggregation sites also tends to provide some protection for spawning segments of other species of fishes. Johannes (1998) says that "more than 40 species of reef fish spawn at the three aggregation sites" of groupers he studied. The spawning of these additional species is not limited to the grouper aggregation site, but protection of a site, as opposed to a species, means that other fishes derive secondary protection.

Fostering (the right type of) Protection

Many instances of disappearances of spawning aggregations are known (Sadovy and Domeier, in prep). In most cases fishers of a given aggregation have been aware of the declines leading to the extirpation. Sometimes the loss is rationalized by saying the fish have moved elsewhere or were disturbed and don't come anymore. While these are possible, most likely the aggregation has been fished out and most fishermen know it. In many cases, calls for protection come from those who suffer most from the loss, the fishers themselves. This is particularly true of older fishermen, who have a longer experience and have more likely seen an aggregation fishery in its prime.

In the last decade, the importance of spawning aggregations to fishery success and the level of exploitation in many areas have raised awareness, at least among monitoring agencies, of the importance of spawning aggregations in many species used for human food. Awareness needs to be raised at the level of government and the individual fisher. Without the support of fishers, it is considerably more difficult for government to put in place the controls needed to prevent loss of aggregations and ultimate decline of the fishery.

To encourage protection, communities need to identify with local aggregation sites as "theirs" and something to protect for their own sake. Certainly any community fishing the area where fishes are drawn from to spawn at the aggregation has a stake in the future of that aggregation. This is why tagging studies can be particularly important for making people realize that the fate of the aggregation affects both their short-term ability to catch fish (none will be left if the entire aggregation is fished out) and the long-term health of the fishery of the aggregating species. Such studies are also important to illustrate how far fish can move and that over-fishing an aggregation in one community can affect catches in the non-reproductive season in a distant community.

Spawning aggregations within marine parks have potential value added components. Ruitenbeek (2001) reported that the value of spawning aggregations within the Komodo National Park, Indonesia was roughly $600,000 USD at 100% protection, a level similar to the direct recreational value of the park, famous for the Komodo dragon. Sala et al. (2001) determined that dive tourism on aggregations in Belize could be worth 20 times the value of extracted fish. However, care is needed before blindly converting an aggregation into a tourist attraction in case uncontrolled disturbance should have a negative impact on reproduction or tourist dollars bypass local communities. Studies can be conducted to determine such potential impacts.

Figure 60. Groupers such as this marbled grouper, Dermatolepis inermis, from the Florida Keys are often thought to be rare, because they are seldom seen. They may just occur in an environment that is seldom fished or visited by divers, but they may also have had their populations driven down by fishing pressure. Determining such things is one of the hardest aspects of working on species of fishes that aggregate to spawn.

It is also essential to look at fisheries of those species that aggregate in their entirety and not to solely focus on the aggregation. In many cases fishing pressure occurs on both aggregated and non-aggregated individuals, both of which may be important to consider when examining population status and determining appropriate management.For example, managing an aggregation of a species that is also heavily fished at other times may ultimately contribute little to the overall problem of over-fishing of the species. As just one possible example, in Palau, aggregations of Plectropomus and Epinephelus were found to be predominantly males, to the point that any females in the aggregation were continuously harrassed by the many males (Johannes et al., 1999). This may have disrupted spawning, although the spawning behavior of the species involved is not well known. The question also arises over how such a distorted sex ratio could occur. Johannes et al. (1999) did not have an explanation for this, but speculated perhaps that this might have resulted from heavy fishing of females at non-aggregated times in more built-up, and therefore, more heavily exploited areas. This emphasizes a point that is often not explicitly considered: that changes to aggregation numbers, sexes and fish sizes at aggregations could also result from non-aggregation fishing pressure. This means that the entire fishery often needs to be considered for management, research or other interventions.

Education Issues

Although historical data on aggregation status is critically important for understanding the effects of targeting these gatherings, video is one of the most powerful ways to convey the message of the fragility of spawning aggregations today. Videos could include interviews with fishermen telling of their experiences, particularly older fishermen who are likely to have seen many changes in their lifetime. Video should have underwater and spawning footage if at all possible since most fishermen have probably never seen aggregations underwater and are unlikely to have witnessed spawning. It is, of course, important to explain scientific work in a simple manner but everybody understands the reproductive imperative and so spawning aggregations represent an excellent opportunity to teach of the importance of allowing fish to reproduce to replenish their kind.

A second video might be prepared to assist fishermen or divers who want to help on a project. One of us (PLC) previously used a video showing people how to remove gonads and otoliths for grouper work in the Gulf of Mexico.

Sociological Issues

Support from fishers is of the utmost importance to the long-term success of protecting aggregations. It is important to communicate the results of studies on aggregations to the fishers involved. This is usually not easily done, but when it can be shown clearly that aggregations are of benefit to retaining local populations, this may drive home the message that is in the fishers own best interests to conserve the aggregation.