Juvenile Pacific bluefin tuna (PBT, Thunnus orientalis) are known to migrate from western Pacific spawning grounds to their eastern Pacific nursery grounds in the California Current Large Marine Ecosystem, but the timing, durations, and fraction of the population that makes these migrations need to be better understood for improved management. This new study published in the ICES Journal of Marine Science suggests that analyzing the trace elemental composition of bluefin tuna otoliths may divulge the time of arrival of the juvenile fish on the Californian Shelf. Scientists from the University of Connecticut, Stony Brook University, Texas A&M, as well as from NOAA collaborated in this effort, hoping to further develop this method to better inform managers in the future.
Baumann, H., Wells, R.J.D., Rooker, J.R., Baumann, Z.A., Madigan, D.J., Dewar, H., Snodgrass, O.E., and Fisher, N.S. (2015) Combining otolith microstructure and trace elemental analyses to infer the arrival of Pacific bluefin tuna juveniles in the California Current Ecosystem. ICES Journal of Marine Science 72:2128-2138.
We have started recording pH, dissolved oxygen, temperature, and salinity in Mumford Cove, using our lab’s brand-new Eureka Manta Sub2 probe. Just in time, because soon we expect the arrival of spawning ripe Atlantic Silversides in the Cove. Thanks to Charlie Woods for the smooth boat ride from and to the institute.
The motto of the 24th Annual Citizen Summit, organized by Save the Sound was ‘Coming back from the brink’. Speakers highlighted the tremendous amount of work towards reducing the eutrophication problem of Long Island Sound, but also the challenges ahead. Baumann highlighted that in addition to traditional concerns of hypoxia as a negative consequence of eutrophication, acidification is a co-occurring stressor. The combination of these two stressors needs to be better understood and tested, because in ecology the effects of two co-occurring stressors may not simply be the sum of each stressor acting alone. Sometimes … 1 + 1 > 2. Other panelists were Dr. Jamie Vaudrey (UConn) and Lisa Suatoni (NRDC) moderated by Dr. Johan (Joop) Varekamp (Wesleyan University and Chairman of the Board, Connecticut Fund for the Environment).
When hearing and talking about sustainable seafood, issues such as overfishing, fishing-related habitat destruction (e.g., trawls tearing through bottom habitat, dynamite fishing) or changes to the architecture of marine ecosystems (‘fishing down the foodweb’) often come to mind. Baumann talked about another potential effect of heavy decade-long commercial fishing, which is less clear but perhaps even more insidious. Nature’s age-old rule of survival in the ocean, i.e., that faster growing fish have better chances of survival, is suddenly reversed when size-selective fishing becomes the dominant agent of mortality. Because in fishing, a faster growing fish will just be susceptible sooner to get caught by the meshes of a fishing trawl. We instinctively know that life on earth has adjusted before to changing selection pressures, and there’s little reason to suspect that this case might be different. Commercial fishing may trigger fisheries-induced evolution, and this may mean smaller, earlier maturing fish and less total biomass for centuries to come. The brief talk will summarize the problem as we know it, explore alternative explanations and look at examples, which show that the issue is also inextricably linked to all the other natural and man-made changes (warming, food web) that affect fish stocks. A cautionary approach that considers evolutionary processes within the framework of sustainable fisheries is surely warranted.