New study links declining Bermuda Spiny Lobster Fishery to changes in the ocean ecosystem far offshore

New study links declining Bermuda Spiny Lobster Fishery to changes in the ocean ecosystem far offshore

As Bermuda’s spiny lobster season opens this September, one of the island’s most prized local delicacies returns to menus and dinner tables. But new research suggests its future may be shaped by changes taking place far beyond Bermuda’s waters.

The Department of Environment and Natural Resources notes that the spiny lobster is a key part of the island’s fisheries economy, representing 10% of fishery landings by weight and 13% by value, and an important source of fishing income in the winter months.

However, the department’s records show that Bermuda’s lobster catch has fallen substantially over the past decade, in terms of both total catch and the average number of lobsters caught in a standard trap deployment, known as catch per unit effort. This decline has occurred despite longstanding management measures that support fishery sustainability, including seasonal restrictions to protect breeding lobsters and regulations that prohibit the capture of juvenile lobsters. 

Now, a study led by the Arizona State University Bermuda Institute of Ocean Sciences researcher Leocadio Blanco-Bercial, and published in Communications Earth & Environment, suggests that the decline of Bermuda’s spiny lobster fishery may be linked to fundamental changes taking place hundreds of kilometers offshore. 

The study, “A simple trophic transfer index predicts spiny lobster fishery dynamics,” brings together long-term fisheries records, ocean observations, and satellite measurements to examine how changes in the offshore marine environment may influence lobster populations around Bermuda.

The larvae of the Caribbean spiny lobster (scientific name Panulirus argus) spend six - nine months drifting in the open ocean, feeding within the plankton community, before eventually settling into shallow water habitats such as mangroves, seagrass beds or coral reefs. The number of young lobsters reaching Bermuda is therefore strongly influenced by ocean conditions across the wider North Atlantic and Caribbean region. 

The new research combines catch and catch per unit effort records from Bermuda’s commercial lobster fishery, contributed by DENR, with long-term observations from the Bermuda Atlantic Time-series Study at ASU BIOS, and satellite measurements of photosynthesis in the ocean. By bringing these datasets together, researchers developed a new index that tracks changes in the ocean and the plankton food chain, and links these changes to impacts on the supply of larvae needed to replenish Bermuda’s spiny lobster population. 

The authors found that the regional ocean has been warming while the amount of photosynthesis, measured via satellite images of pigments such as chlorophyll, has declined. At the same time, changes in the plankton community suggest that the transfer of energy up the food chain is becoming less efficient, resulting in less overall nutrition being available to larger planktonic animals like the lobster larvae. 

The new ‘trophodynamic index’ developed by the researchers combines all these factors. This index explained changes in lobster catch rates better than temperature, primary production alone, previous catch levels, or long-term average conditions. Forecasts based on the index also outperformed these alternative approaches.

“Sustainable fisheries management depends on understanding not only what is happening within the fishery, but also the environmental conditions that influence critical parts of the life cycle of our fishery target species,” said Tammy Warren, senior marine resources officer at the DENR, Government of Bermuda. “As our ocean changes, integrating different types of evidence will become increasingly important to making informed decisions about the future of our marine resources.”

Joanna Pitt of DENR added that, “Most fishery monitoring is based on looking at changes in the catch after those changes have happened. The major benefit of this index is that it can give us some advanced warning of changes that are affecting the early life stages of the spiny lobster, so that we can be prepared to adjust our management approaches.”

Decades of observations from ASU BIOS’s BATS program, fisheries records, and satellite data together provide clearer evidence of how changes in the offshore ecosystem affect local fisheries. Lead author Blanco-Bercial, associate professor with the ASU School of Ocean Futures in the ASU Global Futures Laboratory, noted that the most exciting aspect of the work is “combining data from Bermuda’s fishermen and fisheries with long-term observations from BATS and satellite observations.” By bringing these vital sources together, the researchers can convert decades of scientific data into a format that helps to better understand and predict changes in marine resources.

The trophodynamic index provides an independent indicator of ecosystem conditions that affect a particularly vulnerable stage of the spiny lobster life cycle. However, the complex life cycle of this species presents additional challenges, since juvenile lobsters depend on habitats like mangroves and seagrass beds that are not as abundant as they used to be. The new index is therefore not intended to replace existing fishery monitoring or management tools, but can complement current approaches, improve forecasts, and support more ecosystem-based fisheries management.  

As Bermuda considers the future of its fisheries, this study highlights the importance of combining long-term observations and fisheries data with collaboration among scientists, government, and the fishing community. Together, these efforts can strengthen Bermuda’s ability to anticipate change and support sustainable, ecosystem-based fisheries management.

This work was funded by a Simons Foundation International grant administered by the Simons Foundation.