Collapsing fisheries? Maybe it's starvation, not overfishing.

Some years back, researchers in Honolulu learned that the trick to raising mahimahi in captivity was figuring out what they ate when they were still tiny larvae.

Now University of Hawai`i researchers are among those who have developed similar information about wild fish in the deep ocean. Maybe, they suggest, it isn’t overfishing that’s destroying fisheries, but starvation of the keiki.

(Image: The copepod Calanus finmarchicus, superimposed on a map of the Gulf of Maine. credit: Patrick Hassett, Ohio University.)

Petra Lentz and Andrew Christie, researchers with Pacific Biosciences Research Center at the University of Hawai‘i at Mānoa, are among the authors of a new paper that looks at the collapse of the cod fishery and other fisheries in the North Sea. 

The paper has the unwieldy title, “De Novo Assembly of a Transcriptome for Calanus finmarchicus (Crustacea, Copepoda) – The Dominant Zooplankter of the North Atlantic Ocean.”

Like mahimahi, when they’re still babies, cod eat tiny oceanic crustaceans called copepods. And recently, the species of copepod that cod larvae prefer have themselves been in collapse. That same copepod is a major food source for other creatures as well, including right whales and Atlantic herring. And since bluefin tuna feed on herring, it's at the base the food chain.

So maybe focusing on regulating the fishermen isn’t the answer to restoring fisheries. Maybe you need to look at what’s starving their babies.

The researchers have developed a new genetic technique for assessing what’s going on with the health of the copepods. It’s very technical stuff, but using an approach called transcriptomics, they can study how the copepods’ cells respond to changes in their environment.

And as they learn how that works, they hope to be able to determine which environmental changes are impacting the copepod health—for instance, whether it's ocean acidification, or changes in water temperature, or altered current patterns, or something else.

The researchers are assuming that something in their environment is preventing the copepod, Calanus finmarchicus, from completing its life cycle. And that means that when cod larvae go looking for breakfast, the table is bare.

Several presentations at the 2014 Ocean Sciences Meeting at the Hawai`i Convention Center in late February described the new techniques, which were developed, in addition to Hawai`i researchers, by team members from Ohio University and Indiana University’s National Center for Genome Analysis Support. Mount Desert Island Biological Laboratory in Maine and the University of Georgia Genomics Facility.

The University of Hawai`i news release on the research is here. 

Citation: Lenz PH, Roncalli V, Hassett RP, Wu L-S, Cieslak MC, et al. (2014) De Novo Assembly of a Transcriptome for Calanus finmarchicus (Crustacea, Copepoda) – The Dominant Zooplankter of the North Atlantic Ocean. PLoS ONE 9(2): e88589. doi:10.1371/journal.pone.0088589

© Jan TenBruggencate 2014