How many beluga whales are there in that school? A new method.

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Smaller species of swimming marine mammals are often hard to count because they might be present in ones or twos or in groups of hundreds of individuals. Typical survey methods face multiple types of bias when trying to count total numbers because some individuals are missed. For aerial surveys, this is particularly problematic: individuals in a school can be missed because they are diving, too close to other individuals to be seen, or too far away to be detected in photographs or videos. In addition, some observers systematically over-estimate school size while others systematically under-estimate school size. Now a new method has been developed that takes into account all of the uncertainty associated with these various forms of bias, to better estimate school size. When applied to endangered beluga whales in Cook Inlet, Alaska, the new method estimated that only 55% of individuals are near to the surface during each aerial survey pass, and that 2% of whales are concealed by being close to other whales. Group sizes were highly variable from year to year, with large groups of more than 300 whales detected in some years, while in other years there were lots of small groups of whales. The new methods were developed by SAFS research scientist Charlotte Boyd, SAFS professor André Punt, and coauthors from the Marine Mammal Laboratory, NOAA, and appears in the journal Marine Mammal Science.

Estimated group sizes of beluga whales in Cook Inlet, Alaska, for each survey year.

Sea otters diversify their diets as their numbers grow

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Due to hunting, sea otters were extirpated from most of their former range, including all of Washington state. In 1969 and 1970 a small group of 59 sea otters from Amchitka Island, Alaska, were reintroduced to the outer coast of Washington state, where they have since flourished to more than 2000 individuals. As their numbers have increased, they have expanded along the coast, resulting in a patchwork of locations containing sea otters that have been present in each location for differing lengths of time and at a range of densities. The resulting gradient of occupation time and density provides a natural experiment that a group of researchers has now used to detect which factors affect sea otter diet. The most important predictor for diet was habitat type; in addition, sea otter diet became much more diverse in areas with high sea otter densities, and total energy intake slowed down in high-density areas. The new work by SAFS PhD student Jessica Hale, SAFS and APL professor Kristin Laidre, and their coauthors, appears in the journal Marine Mammal Science.

Jessica Hale
Sea otter mother and pup.
Jessica Hale
Close-up of a sea otter.

Testing the impact of dam passage on homing success in salmon

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Snake River salmonids are federally protected, but face a succession of dams to navigate from the ocean to the spawning grounds. The final dam in the sequence is the Lower Granite Dam. Ascending salmonids (sockeye salmon, steelhead, and Chinook salmon) all enter the fish ladders on the side of the dam, but some pass straight through and exit above the dam, while others are shunted off to one side and either released after a longer pathway, or held in tanks and sampled before being released to continue up the fish ladders. These three different passage routes allow for a statistical analysis to detect whether their homing success is affected by the sampling method, revealing that free passage is better than shunting, but that trapping did not affect detection rates in spawning areas compared to those that were shunted but not trapped. However, since a substantial fraction of salmonids are held in tanks for 15-20 hours before sampling, and these had lower homing success than those held for short periods, it would be wise to alter the trapping protocols to reduce the holding time. The new work by Christina Morrisett and Prof John Skalski of SAFS, and Russell Kiefer at the Idaho Department of Fish and Game, appears in the North American Journal of Fisheries Management.

Arctic lakes play a smaller role in releasing ancient carbon than previously thought

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The dry northern reaches of Earth contain nearly half of all of the carbon originating in living matter, mostly stored in the frozen soils of the permafrost. It has been long thought that warming in the Arctic will result in this carbon being released from the soil and activated again, through the many lakes that are prominent features of the Arctic. Now, a new study shows that more common lake-dominated landscapes in the Arctic do not in fact activate carbon. These lakes in flat and dry regions of the Arctic, making up a quarter of the Arctic, actually have food webs that rely mostly on carbon obtained from the atmosphere, and not on carbon obtained from the long-frozen soil. The new work was led by Matthew Bogard of the School of Environmental and Forest Sciences at the University of Washington, included SAFS professor Gordon Holtgrieve among the coauthors, and appears in the journal Nature Geoscience.

Previous studies in the Arctic have focused on lakes where thawing permafrost plays a large role and comprise only 9% of the northern landscape (beige circles), but the new study focuses on arid and flat landscapes that make up more than a quarter of the northern landscape (red circles).

Shifting newspaper headlines on what makes for a ginormous fish

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Shifting baselines is the concept that each human generation thinks “normal” conditions are those when they were growing up, and therefore only takes into account declines during their lifetime, instead of over multiple generations. A new paper now examines newspaper headlines over time to see whether declining fish size is detectable in fish described as superlatively enormous (e.g. “giant”, “huge”, or “monster”), finding declines in reports of lengths. For the most charismatic species there was evidence that the sizes of fish described as enormous had declined (e.g. basking sharks, whale sharks, giant mantas), but for oceanic sharks and gamefish such as marlins and tunas, there was no decline. One notable finding is that the enormous fish described in headlines are on average only 56% of the maximum length of their respective species. The study suggests that the continued use of superlatives in newspaper headlines may contribute to an incorrect perception that large fish are still abundant in the oceans, even when they are not. The paper was led by Fiona Francis and Brett Howard, other authors from Simon Fraser University, and SAFS professor Trevor Branch.

Changes in relative length of fish described as superlatively large in newspaper headlines over time.
Changes in length and weight of all fish described in superlative terms in newspaper headlines.

Helping bird science while walking along the beach: lessons from 17 years of the COASST project

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Citizen science, where the nonexpert public joins in freely to produce useful science, has grown to more than 2100 projects on the SciStarter website alone. These projects range from online identification of astronomical objects, to gaming-like projects predicting how proteins will fold (Foldit), to seasonal bird counts. One long-running project is COASST (Coastal Observation and Seabird Survey Team) where members of the public conduct monthly surveys of beach areas from California to Alaska looking for bird carcasses. Any found are photographed, tagged, and identified using a key, and the resulting data have been hugely influential in identifying mass bird die-offs on the west coast of the US, among other findings. A new study has now examined which factors lead to high effort, accuracy, and social connectedness in the COASST project. Unlike most online citizen science projects, where >90% of participants drop out after one event, more than half of  COASST participants were still conducting beach surveys more than a year after they joined the project. Bird identification accuracy was 88% overall, and increased rapidly as more carcasses were encountered. Interestingly, many (34%) long-term participants never even found a single carcass, but continued to report their search effort, providing valuable data on bird occurrence and absence. Participants also ranged widely in their social nature, from loners to those who walked mostly in pairs, to those who were highly connected and recruited many others to join in the COASST project. The results show that high-quality data can be successfully collected by extensive citizen science projects, greatly expanding the reach of science. The new work was led by SAFS professor Julia Parrish together with Timothy Jones, Hillary Burgess, and Yurong He at SAFS, Lucy Fortson at the University of Minnesota, and Darlene Cavalier at Arizona State University, and appears in the journal Proceedings of the National Academy of Sciences, USA.

Figure 1: The learning curve of participants in COASST, showing how the accuracy at identifying carcasses to the correct species increases with experience.

 

Figure 2: The larger social networks in the COASST project, showing how some people are connected with large groups, and have recruited many others to join in their surveys, who have in turn recruited others.

Variability in body growth is an important part of variability in fish populations

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It has long been established, indeed it is almost axiomatic, that annual variability in births of new fish (“recruitment”) is the most important reason why the total mass of fish populations varies from year to year. The rate of which individual fish grow (“body growth”) is also known to vary from year to year, but is generally considered to be fairly unimportant in explaining population variability. Now, though, a new study examines the contribution that recruitment and body growth play in fish population variability, finding that for 2 of the 8 fish populations examined, fish biomass varied more because of body growth, while for 5 of the 8 fish populations, fish biomass varied more because of recruitment. Thus more attention should be paid to measuring annual changes in body growth, since this is potentially a key part of understanding why fish biomass varies so much from year to year. The new work by SAFS graduate student Christine Stawitz and SAFS professor Timothy Essington, appears in the Journal of Animal Ecology.

A new guide on how to figure out which parts of DNA are actually expressed

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Scientists trained in ecology and physiology are increasingly able to complement their work with the burgeoning field of “functional genomics”, i.e. the study of which parts of DNA (the “genome”) are actually expressed and used to make proteins under different conditions. A new guide is now provided for those from non-genetic fields to harness the power of fast computers and rapid technology in sequencing the letters in DNA, so that they can infer how animals respond to the environment. One area of particular interest is epigenetics, which refers to changes in gene expression without a change in the DNA letters (e.g. DNA methylation). The new guide outlines what is needed for those interested in using functional genomics, from experimental setup, to the preparation of samples, the use of computers, and final in determining which parts of the genome are expressed under different conditions. The new paper by SAFS professor Steven Roberts and SAFS postdoc MacKenzie Gaverie appears in the Journal of Shellfish Research.

The blue-backed basslet, a new species from the Honduras

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Reef fish species from waters deeper than 130 m are difficult to collect manually, because they are too deep for SCUBA divers. But now manned submersibles equipped with underwater vacuums are able to suck up new specimens with surprising alacrity. Among the specimens slurped up by one such submersible is brand new blue and gold species of basslet: the blue-backed basslet (Lipogramma adabeli), with distinct blue coloration, genetics, and habitat use distinguishing it from other similar species. The new species was described in Zookeys by SAFS professor Luke Tornabene, Ross Robertson of the Smithsonian Tropical Institute, and Carole Baldwin of the Smithsonian Institute.

Photographs of three specimens of the blue-backed basslet, a newly described fish species.

 

The manned submersible used to collect the new species of basslet, complete with suction devices in the front.

Designing salmon-friendly dam turbines

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The Columbia River used to host returns of nearly 9 million salmon every year, led by the largest returns in the world of Chinook salmon (4.4 million fish). But construction of multiple large dams on various tributaries and the Columbia River itself, eliminated salmon from vast tracts of rivers above impassable dams, and also had a serious effect on salmon survival in the remaining areas. Hydroelectric dams have a major impact on the passage of young salmon heading out to the ocean, since some do not survive passage through their electricity-generating turbines. A new review now highlights all of the screening mechanisms designed over more than 30 years in the Columbia River, intended to ensure that outmigrating salmon do not pass through the turbines. One of the key lessons learnt is to first model fish behavior under different river speeds before designing new screening systems to divert salmon around the turbines. The new work was led by SAFS affiliate professor John Williams and by Michael Gessel, Northwest Fisheries Science Center (retired), and appears in Marine Fisheries Review.

Dams in the Columbia River system, showing regions in gray rendered impassable to salmon by dams, and the locations of dams themselves.