Commercially Important Species at Glover’s Reef

Georges Dawson collecting conchs for Charles Acosta and his studenst to tag.

Dr. Charles Acosta was back at Glovers Reef continuing his research on the efficacy of a Marine Reserve on commercially important species. Charles Acosta has been a WCS research associate since 1996 and has been doing field work at Glovers Reef for the past 10 years. His website: http://www.nku.edu/~acostac/research1.html

He was accompanied by two of his students from Northern Kentucky University, Liza Hernandez and Anthony DiBello and a student from the University of Belize, William Mendoza.

Clockwise: Liza Hernandez, Anthony Dibello, Charles Acosta, William Mendoza

Introduction to the project

Charles Acosta has been studying the design and function of marine reserves for the protection of tropical marine biodiversity and heavily-fished populations.
The most recent project aims to show two functions of a Marine Reserve:
· Protection of species with commercial value and which are targeted by local fishery
· Spill-over effect: are the protected species traveling out of the reserve and helping maintain the fishing industry?

To study this Charles Acosta is looking more closely at the population dynamics of commercially-exploited species (spiny lobsters, queen conch, and fishes) in the Glover's Reef Marine Reserve. He is particularly interested in the spatial ecology of these species and the dynamics of the refuge populations and adjacent fisheries

Methods

Charles Acosta and his team spent a week tagging conchs, lobsters and fish.

Conchs

Nearly 1000 conchs were tagged in the Marine Reserve. The location and size of the conch was also recorded.
The next step is to wait for the conchs to be collected by fishermen and tags returned. With the help of Danny Wesby and Georges Dawson (WCS) it should also be possible to know the area where the conch was collected. This way the distance traveled, and the proportion of conch traveling outside the reserve (spill-over effect) can be estimated.

This tagging experiment will also allow to verify a mathematical model created for the conch population of Glover’s Reef during previous field work at Glovers Reef.

Measuring the max length, lip size and width of a tagged conch.

Lobsters

The same protocol is used to study the spill-over effect of lobsters. The tag is placed on the head, which has no commercial value to the fishermen. Again the next step is to wait and see where and how many tags are collected.

Fish

The same protocol is used for the commercially important species of fish. However this group is more challenging because it is much harder to catch these species for release.

Parallel project

Liza and Athony are conducting a parallel project. They are collecting otoliths from the heads of commercially valuable fish (fishermen are asked to keep the heads of fish they filet before selling).

To explain the role of otoliths here is an extract from the Otolith Research Laboratory http://www.marinebiodiversity.ca/otolith/english/home.htm

“Otoliths ("earstones") are small, white structures found in the head of all fishes other than sharks, rays and lampreys. Otoliths provide a sense of balance to fish in much the same way that the inner ear provides balance in humans. Fish otoliths also aid in hearing.
To the fisheries biologist, the otolith is one of the most important tools for understanding the life of fish and fish populations. Growth rings (annuli) not unlike those of a tree record the age and growth of a fish from the date of hatch to the time of death. Daily growth rings formed in the first year of life, and visible only through a microscope, record daily age and growth patterns in surprising detail. And sophisticated chemical techniques allow the reconstruction of everything from the year of hatch, to migration pathways, to the temperature of the water. Indeed, virtually the entire lifetime of the fish is recorded in the otolith.”

Here Liza and Anthony will look at otolith to see where the fish at Glover’s Reef are coming from and where they are spending their different life stage. This will provide information on the role of the Marine Protected Area in protecting fish through their different life stages.

More pictures...

Charles Acosta looking for a conch

Liza, close to the reef crest looking out for a nurse shark!