Juvenile Reef Fish Study
Researchers study Juvenile reef fish to evaluate the population.
Many species of fish caught in the Gulf of Mexico spend the early part of their lives in seagrass beds in the bay. The most important of these species include gag grouper, lane snapper, and gray (mangrove) snapper. The grouper spawn in late winter and juveniles arrive in the bay in late spring. The snapper are early summer spawners and their offspring arrive in the middle of summer. When the juveniles arrive in the grass beds, they are less than ½ inch long and use the grass as both a place to hide to avoid larger fish and a place to hunt for food (usually small shrimp).
By using a small trawl to collect juvenile grouper and snapper in the grass beds, we can evaluate the size of each year’s production and predict how many grouper or snapper will be available to fishermen a few years in the future when the juveniles grow into adults. This predictive capability helps fishery managers adjust the regulations to avoid shortages of these species in the future. The number of fish produced each year fluctuates widely; we have seen 20 times the number of snapper and grouper in one year compared to the number the year before or after. Our sampling method uses short tows of less than one minute and all fish are quickly measured and released alive (95 to 98 percent survival) to minimize our impact on the resource.
Methodology
Methodology followed for the juvenile reef fish study:
-
Knot tied at the end to close the net.
-
Deployment of trawl net near buoy marker.
-
Motoring away from buoy to 50 meters at 2 knots while trawl is towed behind boat.
-
Retrieval of trawl net onto the boat.
-
Measurement of the distance from the boat to the buoy with the laser rangefinder.
-
Samples transferred to tray.
-
Separation of snappers and groupers.
-
Measurement of snappers, groupers, and flounders.Then release.
-
Measurement of water temperature and salinity with a YSI-30 meter.