Reef Fisheries

Much of the fish that supplies local markets and personal consumption in Palau is caught from the near-shore barrier reef and lagoon. However, it is widely regarded from long-term fishermen that the abundance and size of reef fish have decreased in the last two decades. Fortunately, there has been renewed interest in fisheries management to stem the decline.

To best guide management decisions, we need to understand the status of the stock along with biological information to determine the growth and maturity of the many species caught. To assess the stocks with limited information, data-poor stock assessment techniques have been developed to help bridge the gap between the expensive data-rich assessments conducted only for the most valuable fisheries in the world, and the vast majority of smaller fisheries, especially those on coral reefs that support millions of fishers. Data-poor stock assessment methods in its simplest form require information on the size structure of the population along with an estimate of local size at maturity and or asymptotic length.

At CRRF we are involved in fishery data collection to help address knowledge gaps that can preclude effective management of reef fisheries. We employ novel technology to improve the efficiency of data collection and can provide accurate species identifications for the hundreds of species caught on coral reefs in the Pacific. We are currently working on determining the size at maturity of important commercial species and using new methods to answer these questions efficiently.

Dr. Steven Lindfield is the lead on reef fisheries projects, coming from a commercial fishing family in Australia; he has been studying coral reef fish and fisheries in Micronesia since 2010.

Current projects

Validating Underwater Stereo-video for Determining Life-history Parameters of Aggregation Spawning Coral Reef Fishes

We are currently finalizing a Saltonstall-Kennedy competitive research grant which was used to develop a non-destructive, cost effective and accurate methodology to generate reliable local data on the size of maturity of reef fishes. We have been able to do this by utilizing the natural occurrence of fish spawning aggregations to separate immature and mature fishes in a population and gather accurate lengths of these fishes using underwater stereo-video techniques. We have been using this grant to validate the accuracy of stereo-video method by comparing the length frequencies at fish spawning aggregations to the size at maturity calculated from biological sampling of fish gonads and histology. There are twelve species of reef fish we have been able to gather length frequencies from spawning aggregations and also sample gonads from fish markets to estimate size at maturity. These values will also be used to update stock assessments and proposed size limits on these commercially valuable species.

Palau’s Reef Fisheries: Changes in Size and Spawning Potential from Past to Present

This project first analyzed stereo-video footage collected by Steve Lindfield and the Bureau of Marine Resources at the main reef fish market in Palau. These data collected over a 3-month period resulted in length measurements of 2,675 fish from 86 different species. These size frequencies were then compared to data collected in the 1980-90s for the main eight species in the catch. A new data-poor stock assessment technique, the length-based assessment of spawning potential ratio (LB-SPR), was then applied to these species and we found the majority of fishery-targeted species in Palau are currently at a low level of reproductive potential or are quickly approaching a level where potential for stock replenishment is impaired. These data will provide a good baseline to track the hopeful recovery of reef fish stocks into the future with increased fisheries management and awareness of the previous declines.