Florida Tech Research Helps Spur New Marine Protected Areas

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New Federal Law Protecting Fish Spawning Grounds Could Benefit Seafood, Sport Fishing

It’s hard to imagine a world without fish, but many sport fish and popular fish for seafood are being taken from the places they spawn. Fish such as grouper and red snapper found in the Atlantic Ocean reproduce in the same place at the same time each year, which means if enough of them are harvested at those sites, there may not be enough offspring to replenish the population. Eventually, they may never be found there again.

Through years of research, a team of scientists, including Florida Tech professor Ken Lindeman, who focuses on sustainable coastal management and policy, have made the case for protecting these spawning spots to ensure there is enough fish for future generations. With help from their findings, which were published in the journal PlosOne, a new federal rule designated five spawning sites off the East Coast of the U.S. as Marine Protected Areas in June.

Lindeman and other scientists who worked on the research recently helped write a piece for the Environmental Science Journal for Teens that explains their investigation into the patterns and habits of spawning fish and how that knowledge may be applied to keep Atlantic fisheries sustainable. You can read the entire piece here, but it is reprinted in part below:

“People all over the world love eating fish, and have been catching them for thousands of years. Fishing is a huge industry that contributes significantly to local economies along the coast. The Atlantic reef fish industry along the southeast coast of the U.S. alone is worth billions of dollars. If we want to keep eating fish, we need to keep local fish populations healthy and protect them from overfishing.

Scientists and economists have suggested (and sometimes already implemented) many “safe zones,” called Marine Protected Areas or MPAs, for fish in areas where they reproduce. But how do we know where exactly these areas are? And when do fish come there to spawn? Do fish return to the same spawning grounds year after year to mate and reproduce? Most importantly, could we design a model that could predict where certain fish would spawn, so that we could protect them better? We looked at over 30 years of fish data to find out.

Methods:

Scientists have been collecting tons of data on Atlantic reef fish over the last three decades. We specifically screened all these data for the following types of information:

  • Fish species, sex, and whether or not they have recently spawned
  • Time of year (season) when spawning occurs
  • Water temperatures
  • Water salinity
  • Water depth of spawning grounds
  • Underwater topography (imagine mapping the height of mountains but just doing it upside down and under water)
  • Moon phase

These factors may be important in determining good conditions for fish to spawn. By analyzing them, we wanted to create models that could predict the location and characteristics of spawning grounds for the following Atlantic fish species: Gray Triggerfish, White Grunt, Red Snapper, Vermilion Snapper, Black Sea Bass and Scamp. Lastly, we tested how accurate our models were in predicting spawning grounds by comparing our predictions to information received from fishermen or collected by other scientific studies.

Results:

Interestingly, we found that most of the fish species we looked at used the same spawning grounds year after year. Sometimes, different species use the same spawning grounds at different times of year. Many fish also have a preferred spawning season. So what about our models – could they really predict under which conditions fish would reproduce? Comparisons to information collected from other sources suggested they worked pretty well. We were able to predict peak spawning conditions for most of the species in our study. For example, we found that Vermilion Snapper like to release eggs in water with temperature between 20.5 and 21.6 C and about 52-63 m deep, just before the new moon in August.

Discussion:

Our study is important because the populations of many fish that humans like to eat are depleted. We believe that protecting fish during spawning is one of the most effective ways to maintain healthy population sizes. But in order to do that, we have to have better knowledge of when and where fish spawn. Then we can establish – or expand – safe zones where fish are protected from being caught during times when they reproduce. These places and times are critical for promoting sustainable fish populations, and help ensure there will be plenty of fish in the sea.

Sometimes, seasonal protection during spawning times makes more sense than protecting certain areas all year long. Finally, despite all the existing studies on fish, it is clear from our analysis that more year round studies of Atlantic reef fish spawning activities are needed to fully understand what is going on. We especially lack information for the winter months because the seas are rougher and it’s harder to do science on boats offshore in the winter. However, some of the most important reef fish species (including most groupers) reproduce in the winter.

Moreover, we found that many fish species have a preferred water temperature for spawning. As we saw for the Vermilion Snapper mentioned above, this temperature range is fairly narrow. And because global climate change is warming not only temperatures on land, but also in the ocean, we need to closely observe how these changing temperatures will impact fish spawning in the future. Only then can we successfully protect all these tasty and valuable fish populations.”

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