Research Report: An examination of reef fish larvae

by Henri Valles, Biologist / Masters student at the Natural Resource Management Program, UWI, Cavehill, Barbados

Marine Reserves in coral reef areas result in several potential advantages to fisheries.

The most important is that they allow for the protection of fish from fishing, which will result in these fish growing bigger in number and size, and therefore reproduce more and in better conditions. They also allow for the protection of coral reefs, which are used as homes by many coral reef fishes, from physical damage which can be caused by fishing activity such as the use of fish pots.

These advantages result in two important things:

Firstly, as fish populations flourish inside the Marine Reserve, fish will eventually move to unprotected areas. The Marine Reserves therefore result in a safe source of fish for the benefit of fishermen.

Secondly, there will be an increase in the number of eggs that are produced by flourishing adult fish, which will result in the increase of offspring (young fish) generated. At this level, it is important to know that most of the reef fishes produce eggs that are laid in the water, and which once laid, drift away with the currents towards the sea. When the eggs hatch, extremely tiny and young fish (larvae) that do not necessarily look like the adults will emerge. They will spend some time in the sea, often not too far away from the coastline, and will ultimately make their way back to the reefs looking for suitable shelter. Many of these tiny fish are very fragile and will die before or even after getting back to the reefs. Indeed, many factors may affect their survival such as the availability of food and shelter, the abundance of predators and competitors, the strength and direction of currents.

The importance of knowing more about the factors that affect these very tiny fish during their journey and which areas these tiny fish come to settle and to successfully grow into adults cannot be underestimated. For example, a protected area with poor numbers of tiny fish coming into it to increase the existing stock will take many years to become efficient. A protected area will not be efficient either if it is located where unfavorable currents make it difficult or impossible for the valuable generated offspring to make it back to unprotected areas to replenish the fish populations for the future benefit of fishermen.

Indeed, populations of fish in the Soufriere Marine Management Area (SMMA) will depend, among other things, on how successful these tiny fish were on finally settling onto the reefs and on knowing more about the role of Marine Reserves at that level. Without any doubt, any information gathered on this issue will be very valuable for the efficient management of protected and unprotected areas and for fisheries in general. This is because we will know much more about which areas receive more of these tiny fish, in which areas these tiny fish settle more successfully and why. Consequently, we will better asses the roles that protected and unprotected areas are actually playing in the conservation and enhancement of fisheries within the SMMA.

A research project funded by the Natural Resource Management Program of the University of the West Indies, with the support and collaboration of the Department of Fisheries, Anse Chastanet’s Scuba St. Lucia and the SMMA will be commencing in October 1999 in the SMMA. This research project will last approximately three months. It will attempt to shed some light about where, when and how tiny fish settle inside some of the SMMA’s protected and unprotected reef areas, and on which factors affect their survival.

The research project will involve the use of traps with a light inside, specially designed to collect samples of some of these tiny fish. They will be deployed at different areas of the SMMA every night and retrieved the following morning during the whole research period.

The understanding and cooperation of fishermen, divers and other users, is critical for the successful implementation of this research, as it depends totally on the good functioning of these light-traps.