Fish body shape holds key to make fishery management cheaper, easier

July 25, 2018, Smithsonian
A fisher from the Utila Cays small-scale fishery in Honduras hooks a yellowtail snapper (Ocyurus chrysurus). This is an important species in both the small-scale and industrial fisheries of Honduras and throughout the fish's distribution, from the southern United States, the wider Caribbean and Brazil. Canty led a team of scientists who worked with local fishers in Honduras to collect yellowtail snapper from their daily catches, either going on fishing excursions with them, or taking samples if the fisher was able to supply the GPS coordinates of the fishing ground where they had caught their fish. The newly published study analyzed three different forensic tools to test their ability to determine where a fish had been caught within small spatial distances, 5 - 60 kilometers. Credit: International League of Conservation Photographers/Claudio Contreras-Koob

A simple body-shape analysis can reveal what part of the ocean a fish came from, according to a new study from Smithsonian scientists working to develop better tools for managing small-scale fisheries. The researchers found that body-shape analysis reliably discriminated between yellowtail snapper caught at Caribbean fishing grounds just 5 kilometers apart—and it did so more accurately than two more costly and technology-intensive techniques.

The research, published July 25 in the Journal of Applied Ecology, was led by Steven Canty, program coordinator for the Marine Conservation Program at the Smithsonian's National Museum for Natural History and researcher with Manchester Metropolitan University. It was conducted in collaboration with scientists at Stanford University, Manchester Metropolitan University, the British Geological Survey and Rare Inc., a conservation organization in Arlington, Virginia.

Small-scale fisheries feed and employ millions of people around the world. Individually, these fisheries remove modest amounts of from the ocean, and they are not usually as closely managed as industrial vessels. Cumulatively, however, their impact on the oceans is profound. In 2010, for example, artisanal fisheries in Honduras caught nearly 10,000 metric tons of fish—more than twice the catch of industrial fleets in the same country.

Careful management is crucial to ensure small-scale fisheries remain sustainable for both the health of the oceans and the communities they economically support. However, their wide distribution and diverse nature have made it difficult to track their catches.

"We really need to start including small-scale fisheries into management," Canty said. "A big part of that is knowing where your fish has come from. If you don't know that, how do you know how productive one bank is, especially over time or over seasons?" Such data is needed to understand the importance of different fishing grounds to local communities and to identify overfished areas that need time to recover.

Two small-scale fishers from Honduras on a fishing trip targeting reef fish on a nearby reef. Small-scale fishers share their fishing grounds with fishers from other communities. Each community may have a different name for the fishing ground, which makes it difficult for fisheries managers to estimate fishing pressure at different fishing grounds. The findings of the newly published study suggest that by using body-shape analysis, fisheries managers can identify the origin of individual fish quickly, cost-effectively and with a high degree of accuracy, making it highly applicable to small-scale fisheries across the globe. Credit: News-media use of these photos in relation to this study is permitted with attribution.

Seeking a practical tool that could be easily implemented even where resources are limited, Canty and his colleagues assessed three different methods for identifying the geographic origins of fish. They focused their study on yellowtail snapper, an economically important species for Caribbean fisheries, and gathered samples from three fisheries located off the coast of Honduras, between 5 and 60 kilometers apart.

The body shape, or morphometric, analysis was the simplest, cheapest and most accessible method included in their study. For every fish, researchers measured the distance between various anatomical landmarks—making 21 measurements in all—and compared these to the overall length of the fish. Because a fish's shape is influenced by the conditions in which it lives, such as ocean depth, currents and diet, this method detected subtle differences in body shape between yellowtail snapper caught at each of the three locations. The team was able to use the method to correctly identify the origins of about 80 percent of the fish in their test sample.

The team also investigated how well they could identify a fish's origins using genetic and chemical tests—in the first case, analyzing the DNA at 15 different genetic markers, and in the second, analyzing the composition of fish ear stones, known as otoliths, that absorb elements from the surrounding water. But these methods were not only more time-consuming, technically demanding and costly, they were less accurate.

The outcome was encouraging, because there are few barriers to implementing morphometric analysis in small-scale fisheries. "You can train anyone to do it," Canty said. "You take a pair of calipers, record measurements and give the fish back to the fisher. They can then sell it, and you can tell where that fish was caught from."

The Smithsonian team and their collaborators are now working with fishers throughout Honduras and Belize to collect body-shape data on yellow snapper from additional fishing grounds. Their hope is that fisheries managers can begin to apply what they have learned sometime next year. Eventually, with further data collection and testing, morphometric analysis could be a useful tool for tracing the origins of many different fish species, Canty said.

Explore further: 437 million tons of fish, $560 billion wasted due to destructive fishing operations

More information: Journal of Applied Ecology (2018). DOI: 10.1111/1365-2664.13230

Related Stories

Recommended for you

Computing the origin of life

December 14, 2018

As a principal investigator in the NASA Ames Exobiology Branch, Andrew Pohorille is searching for the origin of life on Earth, yet you won't find him out in the field collecting samples or in a laboratory conducting experiments ...

Black widow spiders dial up posture for survival and sex

December 14, 2018

A new study led by Western University's Natasha Mhatre shows that body dynamics and posture are crucial to how black widow spiders decode the important vibrations that travel through their webs and up their legs. Black widows ...

To repair DNA damage, plants need good contractors

December 13, 2018

When a building is damaged, a general contractor often oversees various subcontractors—framers, electricians, plumbers and drywall hangers—to ensure repairs are done in the correct order and on time.

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

not rated yet Jul 25, 2018
Good. So, GO FISH AND MAKE THEIR PRICE CLOSE TO ZERO CENTS - They Beat Beef, Pork etc., in maintenance of our Health ; Stop Worrying about your surrounding animals (Adopt DON'T CARE Approach), because for sure, you are going to go away before 90 yrs; Just Avoid Atmospheric pollution only because it affects you also ! Dinosaurs were decimated -- NOT BY Non-Earth Object hitting our planet -- BUT, BY SOME MICROBE That could FOCUS UPON GENE that was COMMON FOR ALL Ancestral DINOSAURS. Expand your Knowledge based upon latest Science....Go & ASK GENETICISTS for AN EXPLANATION for it !

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.