With sea ice loss, beluga whales make longer and deeper feeding dives in the same places

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Satellite tracking devices on beluga whales in the Arctic show how they reacted to far lower sea ice concentrations in recent years. Instead of shifting where they feed, as might have been expected, beluga whales continued to feed in similar (but now largely ice-free) places. However, where dive data were available, their dives were significantly longer and deeper than in years with higher ice concentrations. The research, led by former SAFS graduate student Donna Hauser and Prof. Kristin Laidre, were unable to tell whether the deeper, more prolonged, dives were bad for the belugas (because deeper dives use up more energy), or good for belugas (because they can access new feeding habitat in the absence of sea ice). The research appears in the journal Diversity and Distributions and is highlighted on UW News.

Two graphs
Beluga whales from the Chukchi population had significantly more long dives (top) and deep dives (bottom) in the later more ice-free period (2007-12, blue) than in the early period (1998-2002, red).

Narwhals prefer serene glaciers over rambunctious glaciers

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Combining data from glaciers with tracking devices on narwhals, reveals that these elusive marine mammals prefer glaciers that calve infrequently over active calving glaciers. The research, to be presented by SAFS professor Kristin Laidre at the Ocean Sciences Meeting next week, shows narwhals congregating at the outlets of serene glaciers in Greenland’s Melville Bay. Prof. Laidre speculates that the cold fresh water melting off the glacier may stun fish, making them easy prey for the hunting narwhals, while active glaciers produce more silt-filled waters that are harder to hunt in. The research is highlighted in UW Today.

What is ecosystem-based fisheries management?

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The intent of ecosystem-based fisheries management is to move beyond managing each species separately, and to also consider interactions with other species and ecosystem functioning, as well as human benefits such as food, revenue and recreation. A new paper shows that, in practice, people have very different opinions about which management actions could be classed as ecosystem-based. Furthermore, it is highly unlikely that any particular fishery would be able to meet all of the items on a checklist of possible ecosystem-based actions. Instead, managers should seek to incorporate components of ecosystem-based management that are relevant to the fishery at hand. The new paper was written by SAFS graduate students John Trochta, Maite Pons, Merrill Rudd, Melissa Krigbaum, SMEA graduate student Alexander Tanz, and SAFS professor Ray Hilborn, and appears in the journal PLoS One.

There is a wide range of opinions about whether specific management actions should be classed as ecosystem-based fisheries management, as seen in reactions to the above

When do ecological interactions matter in fisheries?

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Nearly all fisheries management is based on assessing one species at a time, ignoring any interactions with other species. Many have claimed that including these interactions will improve management and lead to greater fisheries profits. A new paper tests whether precise information on species interactions improves economic performance in fisheries. Somewhat reassuringly, economic value was not markedly lower if managers assumed that an incorrect type of interaction was true. But, risk of economic losses were uneven, with the fishery targeting the predator much more negatively affected than the fishery targeting the prey species, particularly when predators are at low abundance. The results show a path forward for managing fisheries using an ecosystem approach instead of a single-species approach: adopt strategies that maintain predator and prey stocks at levels where management decisions are robust to uncertainty about the true state of species interactions. The paper was authored by SAFS professor Tim Essington and appears in the journal Proceedings of the National Academy of Sciences with a commentary by the author here and a UW press release here.

 

Plastic waste in the oceans is linked to disease in coral reefs

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Millions of tons of plastics enter the ocean each year, and many of these end up entangling on coral reefs. Microbes that live on the plastic can then cause coral diseases. A new study appearing in Science today examined more than 100,000 individual corals, finding that only 4% of corals have disease when they are plastic free, but a staggering 89% of corals that are in contact with plastics are diseased. There is an urgent need to reduce the amount of plastics discarded into the oceans each year, but instead the amounts are projected to increase by an order of magnitude by 2025, with alarming possible effects on coral reefs around the world. The research was conducted by an international team led by Joleah Lamb of Cornell University, including SAFS MS student Evan Fiorenza.

The curious tale of the piranhas that merely eat a few scales off their fish prey

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Not all piranhas eat in the feeding frenzies that Hollywood is so fond of depicting. Instead, some species remove and eat just a few scales from their prey. As described in UW News, some of these scale-eaters ram into their unsuspecting prey, while others open their mouths to extraordinary dimensions and use specialized teeth to pry off scales. The wide variety of approaches is captured in a new paper that placed these fish in CT scanners, as part of the Scan All Fish program led by SAFS professor Adam Summers. The scans revealed unprecedented details about how this particular group of piranhas manages to survive and thrive on their rather odd diet. The research was conducted at the Friday Harbor Laboratories by postdoc Matthew Kolman, researcher Kory Evans, SAFS undergraduate Jonathan Huie and SAFS professor Adam Summers, and appears in the journal Royal Society Open Science.

A scanned image of a piranha jaw from the side and front.
The extendable jaws of Catoprion mento, a piranha species that lives entirely by eating the scales off other fish species.

 

Forgotten fish naturalist and illustrator remembered in new book

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Naturalist Charles Plumier’s work has been resurrected by SAFS Professor Ted Pietsch in a new book Charles Plumier and His Drawings of French Caribbean Fishes. Plumier lived in the era just before Linneaus created his Latin naming system for species names, and as a result, none of Plumier’s detailed painting and descriptions of species were given priority. Prof Pietsch talks in detail about the inspiration for his book with Michelle Ma in an interview posted on UW Today.

Costs of processing salmon limit the reward for managing predators and prey together

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In Chignik, Alaska, sockeye salmon are preyed on when young by coho salmon; the sockeye support a valuable fishery, but coho do not. A simulation exercise examined whether fishers and processors might make more money if coho were reduced by fishing, under different levels of predation of coho on sockeye. Models suggested that fishers would end up with higher harvests, and make more money, but processors would probably not benefit because of the extra costs of processing low-value coho salmon. Without processors to purchase additional coho harvest, fishers would have limited short-term incentive to harvest coho. These results highlight the importance of considering the unique constraints and opportunities facing multiple stakeholders when weighing future management options. The work was conducted by SAFS PhD student Timothy Walsworth and professors Daniel Schindler and Timothy Essington and appears in the Journal of Applied Ecology.

Dam removal frees fish to feed in the ocean

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Bull trout in the Elwha River have been separated from the ocean for a century, but dam removal in 2012-14 has now freed them to head out to the ocean again. Analysis of stable isotope ratios reveals that bull trout now spend substantial time at sea eating marine prey before heading back to the Elwha River to spawn. This re-emergence of a long-lost life history variation after being landlocked for so many decades, shows that fish species can swiftly adapt and change their strategies when new opportunities arise. The work by SAFS Prof. Thomas Quinn and his coauthors was published in Environmental Biology of Fishes.