Welcome to our blog series, Research Highlights! On the second Monday of each month, we will debut newly published fisheries research by our women of fisheries colleagues. If you have research you would like to highlight and share with our readers, please contact us at women.of.fisheries@gmail.com.

Our December Research Highlight:
Gleiber M.R., S. Sponaugle, and R.K. Cowen. 2020. Some like it hot, hungry tunas do not! Implications of temperature and plankton food web dynamics on growth and diet of tropical tuna larvae. ICES Journal of Marine Science.

As we approach the winter solstice here in the Northern Hemisphere, maybe you’re like me and dreaming of whisking away to a warmer destination. I think of my counterparts “on the other side” to my south enjoying a long, warm summer-like day. What I wouldn’t do to trade a Polar Plunge for a dip in some nice warm ocean water right now. I know not everyone loves warm weather or even the beach (gasp!), but I am not one of them. Give me sun, long days, and lots of blue therapy!

But alas, reality.

At least we can still talk about fish!

Dr. Miram Gleiber, along with her fellow colleagues at Oregon State University, recently published her doctoral research about larval tuna sampled in the Straits of Florida. That’s just east of the Florida Keys and southern tip of the peninsular part of Florida. From Oregon to Florida, it’s a true coast to coast piece of work.

Before we dive into the paper, though, I have to admit the title is what originally caught my eye (and got me dreaming). It starts with “Some like it hot, hungry tunas do not!” It’s a little more complicated than that, but that definitely got me intrigued.

Over a period of two summers, larval tuna, presumably Blackfin Tuna Thunnus atlanticus, were collected and analyzed for diet and growth. This information was then related back to water temperature and prey data collected concurrently with the fish samples. In these two years, the researchers observed very different conditions: one with lower water temperatures but higher prey availability and one with higher water temperatures but lower prey availability.

It is important that fish grow fast during this early life stage to avoid predation. Typically, these fish would grow faster in the higher temperature scenario, but prey availability turns outs to be an important factor to consider. In fact, in the year when water temperatures were lower, the fish’s stomachs were twice as full and growth was 30% greater than in the year when water temperatures were higher. Researchers also observed a ten-fold increase in the number of fish, so not only were they growing faster and having fuller stomachs, there were also more of them.

So, as with most things in science, the answer is complicated.  As stated by Dr. Gleiber and her colleagues, “Further understanding how larvae respond to multiple aspects of environmental variability is essential in exploring new fisheries and sustainably managing current populations in a changing ocean.”

Which brings to me another question. Why are our oceans changing?

One big reason is climate change.

Warm temperatures may be good for my cold-natured body, but it’s not necessarily a good thing for our planet. Especially when we’re talking about the ocean and the myriad of life that depends on it.

This year, the American Fisheries Society and 110 other aquatic scientific societies issued a joint statement to raise alarm about the effects of climate change on fisheries resources around the world. Thousands of peer-reviewed studies have been published documenting these effects, which range from changes in fish species composition, growth, and behavior to disease to ocean acidification to food trophic level impacts.

Climate change affects us all. We depend on our aquatic ecosystems for food, livelihoods, and even protection. For many (including myself), they also serve as a source of recreation and relaxation. Our lives and the health of our aquatic resources are intertwined.

We may be able to adapt to some of these changes, but others may happen too quickly or be too great to overcome.

How will we know?

That’s where researchers like Dr. Miram Gleiber come into the picture. Each piece of the puzzle adds to our knowledge of how a changing world may impact our natural resources. Specifically, Dr. Gleiber and her colleagues’ research will improve our understanding of the effects of warmer ocean temperatures and prey community shifts on the growth and survival of larval tuna in the future.

This has implications not just for Blackfin Tuna, but other tuna species as well. As top predators in the ocean – and popular food item on our plates – research like this is imperative to the future management of this group of fishes.

And that is pretty “cool” stuff.   

The full manuscript can be found and downloaded here: https://doi.org/10.1093/icesjms/fsaa201

Additional climate change resources are provided by the American Fisheries Society here.