February 5, 2018

Red Snapper Lutjanus campechanus are a highly prized and contested species because of their popularity with both sport and commercial fishers, and stock assessments are critical. Mandy Karnauskas and her colleagues implemented intensive fishery independent surveys that added valuable information on the spatial distributions of different age classes to answer questions their broad- scale demographics and especially how they are distributed among both natural and artificial habitats. They found that, for younger age classes, catch rates were 20 times higher on artificial structures than natural reefs. Those high catch rates had been of great concern, because prior research suggested that the majority (70%) of age-2 Red Snapper were concentrated at oil platforms; their research indicated that only about 3%–7% of fish occurred there. Thus, population fish vulnerability at artificial structures was far lower than thought previously, but managers can also consider fishery effects that concentrate on specific age classes in specific places. That concern occurred because although stock structure was known, no one knew where different age classes occurred, or in what habitats. Their work revealed an unknown dimension to the black box, and will lead to more informed management decisions. Whew! Marine and Coastal Fisheries: Dynamics, Management, and Ecosystem Science is a relatively new journal, but it also has the newest research that makes a difference. Reference: Karnauskas, M., J. Walter, III, M. Campbell, A. Pollack, J. M. Drymon, and S. Powers. 2017. Red Snapper distribution on natural habitats and artificial structures in the northern Gulf of Mexico. Marine and Coastal Fisheries: Dynamics, Management, and Ecosystem Science [online serial] 9: 50–67 

Growing concerns with antibiotic resistance have increased the need for non antibiotic disease treatments. Atefeh Sheikhlar and colleagues challenged Sharptail Catfish Clarias gariepinus with the bacterium Aeromonas hydrophila and compared growth and survival among untreated controls, treatment with the antibiotic oxytetracyline, and varying concentrations of an extract of the Asian asthma- plant Euphorbia hirta that was mixed into diets. They found that, while not as effective as tetracycline, the addition of higher dosages of E. hirta as a dietary additive conferred some measure of disease resistance and dietary addition was an effective disease preventative. Interestingly, it was included for testing because it is used widely in traditional medicine, and chosen because, among a variety of herbal extracts, it had the greatest effect on bacteria at the lowest concentration of any extract they examined. Peer-reviewed tests of alternative fish disease therapies are a hallmark of Journal of Aquatic Animal Health- and are leading the way to healthier fish and fish products. Reference: Sheikhlar, A., G. Meng, R. Alimon, N. Romano, and M. Ebrahimi. 2017. Dietary Euphorbia hirta extract improved the resistance of Sharptooth Catfish Clarias gariepinus to Aeromonas hydrophila. Journal of Aquatic Animal Health 29: 225 – 235. 

Technological advances have led to unprecedented insights into animal movements, and this study by Eric Richer and his colleagues added GPS capability to radio- frequency identification (RFID) tags to accurately determine near- exact locations of fi sh within streams such that far more precise estimates of habitat use are now attainable. As a bonus, it gave precise abundance estimates of tagged fish, and the bigger the system, the more accurate the results. How often does that happen? We feature this paper not only because it was a cool study, but it portrays how cutting edge technology can be both evaluated, and transferred to people who need it to answer management questions. And, by the way, you saw it at North American Journal of Fisheries Management first. Reference:  Richer, E. , E. Fetherman, M. Kondratieff, and T. Barnes. 2017. Incorporating GPS and mobile radio frequency identification to detect PIT- tagged fish and evaluate habitat utilization in streams. North American Journal of Fisheries Management 37: 1249 – 1264.