Real-time reporting of baleen whale passive acoustic detections from ocean gliders.

In the past decade, much progress has been made in real-time passive acoustic monitoring of marine mammal occurrence and distribution from autonomous platforms (e.g., gliders, floats, buoys), but current systems focus primarily on a single call type produced by a single species, often from a single location. A hardware and software system was developed to detect, classify, and report 14 call types produced by 4 species of baleen whales in real time from ocean gliders. During a 3-week deployment in the central Gulf of Maine in late November and early December 2012, two gliders reported over 25,000 acoustic detections attributed to fin, humpback, sei, and right whales. The overall false detection rate for individual calls was 14%, and for right, humpback, and fin whales, false predictions of occurrence during 15-min reporting periods were 5% or less. Transmitted pitch tracks--compact representations of sounds--allowed unambiguous identification of both humpback and fin whale song. Of the ten cases when whales were sighted during aerial or shipboard surveys and a glider was within 20 km of the sighting location, nine were accompanied by real-time acoustic detections of the same species by the glider within ±12 h of the sighting time.

Elevated CO2 alters behavior, growth, and lipid composition of Pacific cod larvae.

High-latitude seas, which support a number of commercially important fisheries, are predicted to be most immediately impacted by ongoing ocean acidification (OA). Elevated CO2 levels have been shown to induce a range of impacts on the physiology and behavior of marine fish larvae. However, these responses have yet to be characterized for most fishery species, including Pacific cod (Gadus macrocephalus). Based on laboratory experiments, we present a multi-faceted analysis of the sensitivity of Pacific cod larvae to elevated CO2. Fish behavior in a horizontal light gradient was used to evaluate the sensitivity of behavioral phototaxis in 4-5 week old cod larvae. Fish at elevated CO2 levels (∼1500 and 2250 µatm) exhibited a stronger phototaxis (moved more quickly to regions of higher light levels) than fish at ambient CO2 levels (∼600 µatm). In an independent experiment, we examined the effects of elevated CO2 levels on growth of larval Pacific cod over the first 5 weeks of life under two different feeding treatments. Fish exposed to elevated CO2 levels (∼1700 µatm) were smaller and had lower lipid levels at 2 weeks of age than fish at low (ambient) CO2 levels (∼500 µatm). However, by 5 weeks of age, this effect had reversed: fish reared at elevated CO2 levels were slightly (but not significantly) larger and had higher total lipid levels and storage lipids than fish reared at low CO2. Fatty acid composition differed significantly between fish reared at high and low CO2 levels (p < 0.01) after 2 weeks of feeding, but this effect diminished by week 5. Effects of CO2 on FA composition of the larvae differed between the two diets, an effect possibly related more to dietary equilibrium and differential lipid class storage than a fundamental effect of CO2 on fatty acid metabolism. These experiments point to a stage-specific sensitivity of Pacific cod to the effects of OA. Further understanding of these effects will be required to predict the impacts on production of Pacific cod fisheries.