Southwest Fisheries Science Center

San Diego, CA, United States

Southwest Fisheries Science Center

San Diego, CA, United States
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News Article | April 17, 2017
Site: www.eurekalert.org

A new study assessing the underwater soundscape off Southern California found that blue, fin and humpback whales experience a range of acoustic environments, including noise from shipping traffic as well as quieter areas within a national marine sanctuary. The study appeared in a special issue of Endangered Species Research focusing on ocean noise. "Our research provides a framework that can be used to evaluate how shipping traffic affects acoustic environments and a tool to explore existing and future management strategies," said Jessica Redfern, a research biologist at NOAA Fisheries' Southwest Fisheries Science Center in La Jolla, Calif., and the lead author of the study. Other authors include scientists from NOAA's Office of National Marine Sanctuaries and Office of Science and Technology, the National Park Service and private consulting companies. The analysis is a case study in NOAA's Ocean Noise Strategy Roadmap, which describes methods of measuring and assessing the impacts of ocean noise. Blue whales feed in Southern California waters from about June to October, while humpback whales feed in the area from March to November and fin whales have been found there year-round. Underwater shipping noise occurs at low frequencies and these three species of large whales are low frequency hearing and communication specialists. Therefore, the potential for low frequency noise to mask communication has been identified as a primary concern. The study used U.S. Coast Guard data on ship traffic from 2009 to estimate sound levels throughout Southern California waters, including areas south and west of Point Conception and in the Channel Islands National Marine Sanctuary. The analysis found that about 95 percent or more of the study area (see the maps) contained noise exceeding references for preindustrial levels. The analysis also found elevated noise levels in important whale feeding grounds and other areas expected to have higher whale densities, especially the Santa Barbara Channel, areas offshore of Point Conception, west of San Miguel Island and south of San Miguel Island and Santa Rosa Island. The analysis also found that some important blue and humpback whale feeding areas overlap quieter coastal waters near Point Conception and in the Channel Islands National Marine Sanctuary. The analysis found both noisy and quieter areas in the Channel Islands National Marine Sanctuary. Noisier areas occur primarily where an established shipping route intersects the Sanctuary's boundaries. Apart from this area, the sanctuary is relatively quiet compared to the rest of the study area (see the maps). Although the Sanctuary does not regulate noise, the quieter areas occur where the Sanctuary is designated as an area for ships to avoid to reduce risks of grounding and pollution. This designation demonstrates that there may be effective strategies to mitigate the risks of noise to marine species, researchers said. "Noise levels appear to be lower within some areas of the Channel Islands National Marine Sanctuary, perhaps providing some respite to whales who have to live in an increasingly noisy ocean," said Chris Mobley, Sanctuary Superintendent. "This analysis framework will help guide our on-going effort to protect whales from direct and indirect interactions with ships."


News Article | February 15, 2017
Site: www.eurekalert.org

California sardine stocks famously crashed in John Steinbeck's "Cannery Row." New research, building on the pioneering work of Soutar and Isaacs in the late 1960s and others, shows in greater detail that such forage fish stocks have undergone boom-bust cycles for centuries, with at least three species off the U.S. West Coast repeatedly experiencing steep population increases followed by declines long before commercial fishing began. Natural population fluctuations in Pacific sardine, northern anchovy and Pacific hake off California have been so common that the species were in collapsed condition 29 to 40 percent of the time over the 500-year period from A.D. 1000 to 1500, according to the study in the journal Geophysical Research Letters. Using a long time series of fish-scales deposited in low-oxygen offshore sedimentary environments off southern California, the authors from NOAA Fisheries and the University of Michigan described such collapses as "an intrinsic property of some forage fish populations that should be expected, just as droughts are expected in an arid climate." The findings have implications for the ecosystem, as well as fishermen and fisheries managers, who have witnessed several booms, followed by crashes every one to two decades on average and lasting a decade or more, the scientists wrote. Collapses in forage fish can reverberate through the marine food web, possibly causing prey limitation among predators such as sea lions and sea birds. "Forage fish populations are resilient over the long term, which is how they come back from such steep collapses over and over again," said Sam McClatchie, supervisory oceanographer at NOAA Fisheries' Southwest Fisheries Science Center in La Jolla, Calif. "That doesn't change the fact that these species may remain at very low levels for periods long enough to have very real consequences for the people and wildlife who count on them." Downturns in sardine and anchovy linked to changing ocean conditions have contributed to the localized stranding of thousands of California sea lion pups in recent years. Scientists traced the historic abundance of sardine, anchovy and hake by examining deposits of their scales collected on the floor of the Santa Barbara Channel from A.D. 1000 to 1500. While previous studies had shown that forage fish exhibited collapses prior to commercial fishing, the new research used methods developed by climatologists to examine the frequency and duration of the fluctuations in finer detail. "The Mediterranean climate of California with wet winters and dry summers produces a sediment layer we can pull apart like pages in a book" says Ingrid Hendy, Associate Professor at the University of Michigan in Ann Arbor. "Although these sediments have been studied before, we are using new technology to examine them in unprecedented detail." The scientists described a collapse as a drop below 10 percent of the average peak in fish populations, as estimated from the paleorecord. Anchovy took an average of eight years to recover from a collapse, while sardine and hake took an average of 22 years. The record also showed that sardines and anchovy fluctuated synchronously over the 500 year study period. Combined collapses may compound the impact on predators and the fishery, the scientists said. The finding runs counter to suggestions that the two species' cycles alternate. Sardines and anchovy have at times been the most heavily harvested fish off Southern California in terms of volume. Hake, also known as Pacific whiting, spawn off California but are harvested in large volumes off the Pacific Northwest and Canada. The new study concludes these forage fish are well-suited to variable fishing rates that target the species in times of abundance, "while recognizing that mean persistence of fishable populations is one to two decades, and that switching to other target species will become a necessity." Collapses last, on average, "too long for the industry to simply wait out the return of the forage fish." The study authors concluded that "well-designed reserve thresholds" and adjustable harvest rates help protect the forage species, the fishery and non-human predators for the long term. However, they added that "reserve thresholds only protect the seed stock for recovery, and cannot prevent collapses from occurring."


News Article | February 15, 2017
Site: www.eurekalert.org

Scientists know a great deal about blue whales off California, where the endangered species has been studied for decades. But they know far less about blue whales in the Northern Indian Ocean, where ships strike and kill some of the largest animals on Earth. Now a research team has found a way to translate their knowledge of blue whales off California and in the eastern tropical Pacific Ocean to the other side of the world, revealing those areas of the Northern Indian Ocean where whales are likely to be encountered. The team of scientists from NOAA Fisheries and the Sri Lankan Blue Whale Project published the findings in the journal Diversity and Distributions. The Scientific Committee of the International Whaling Commission included the results of the study when assessing a shift in busy shipping lanes off the south coast of Sri Lanka that will reduce the danger to whales in an important feeding area. "Small changes in shipping routes can be a very effective way to address a serious conservation issue with minimal inconvenience to the shipping industry, but rely on a good understanding of the relationship between whale distribution and habitat," said Russell Leaper, a member of the Scientific Committee. "This study makes an important contribution towards that understanding." To meet requirements of the U.S. Marine Mammal Protection Act, NOAA Fisheries regularly conducts marine mammal and ecosystem assessment surveys. Surveys off the U.S. West Coast and in the eastern tropical Pacific have shown that the upwelling of deep ocean water rich in nutrients supports dense patches of krill that blue whales feed on. This information has proven critical in addressing the emerging problem of ships striking blue whales, and has informed the management of ship traffic to and from the busy ports of Los Angeles and Long Beach to mitigate this problem. "We are fortunate in the United States to have some of the best marine mammal data sets in the world," said Jessica Redfern, a research scientist at NOAA Fisheries Southwest Fisheries Science Center in La Jolla, Calif., and lead author of the new study. "It was exciting to explore how we could use these data sets to aid conservation efforts in parts of the world where few data exist." The research developed computer models of blue whale habitat off the U.S. West Coast and in the eastern tropical Pacific, including upwelling and underwater topography that affects areas of krill concentration. The models then identified similar upwelling and feeding regions in the Northern Indian Ocean that are also likely to be important habitat for the endangered species. "The Sri Lankan Blue Whale Project has spear-headed efforts to draw attention to and mitigate the risk of ships striking blue whales in Sri Lankan waters. To best protect this species in this data-limited region, it is essential to adapt approaches developed in other parts of the world. Our collaboration achieves just that," said Asha de Vos, founder of the Sri Lankan Blue Whale Project and a coauthor on the study. The Northern Indian Ocean and its inhabitants have not been surveyed to the same extent as the eastern Pacific Ocean, and much of the information about whale distributions comes from Soviet whaling several decades ago. However, the model results matched up well with the limited information available, the scientists reported. The model suggests that the distribution of blue whales in the Northern Indian Ocean may shift seasonally, following their food as monsoon climate patterns alter the most productive habitat. The scientists concluded that research and monitoring is critical in the areas identified as blue whale habitat in the Northern Indian Ocean because many of these areas overlap with some of the busiest shipping routes in the world. "Marine mammals face threats from human activities in most of the world's oceans, but we lack the data needed to address these threats in many areas," Redfern said. "The data collected aboard our surveys allow us to predict species habitat in other parts of the world. Understanding species habitat allows us to address conservation problems that are often unexpected and critical to maintaining healthy populations."


News Article | February 15, 2017
Site: phys.org

Natural population fluctuations in Pacific sardine, northern anchovy and Pacific hake off California have been so common that the species were in collapsed condition 29 to 40 percent of the time over the 500-year period from A.D. 1000 to 1500, according to the study published online Feb. 9 in Geophysical Research Letters. Using a long time series of fish scales deposited in low-oxygen, offshore sedimentary environments off Southern California, researchers from the National Oceanic and Atmospheric Administration and the University of Michigan described such collapses as "an intrinsic property of some forage fish populations that should be expected, just as droughts are expected in an arid climate." The findings have implications for the ecosystem, as well as fishermen and fisheries managers, who have witnessed several booms, followed by crashes every one to two decades on average and lasting a decade or more, the scientists wrote. Collapses in forage fish—small fish that are preyed on by larger predators for food—can reverberate through the marine food web, causing prey limitation among predators such as sea lions and sea birds. "Forage fish populations are resilient over the long term, which is how they come back from such steep collapses over and over again," said Sam McClatchie, supervisory oceanographer at NOAA Fisheries' Southwest Fisheries Science Center in La Jolla, Calif., and first author of the paper. "That doesn't change the fact that these species may remain at very low levels for periods long enough to have very real consequences for the people and wildlife who count on them," he said. Downturns in sardine and anchovy linked to changing ocean conditions have contributed to the localized stranding of thousands of California sea lion pups in recent years. Scientists traced the historic abundance of sardine, anchovy and hake by examining deposits of their scales collected on the floor of the Santa Barbara Channel from A.D. 1000 to 1500. While previous studies had shown that forage fish exhibited collapses prior to commercial fishing, the new research used methods developed by climatologists to examine the frequency and duration of the fluctuation in finer detail. "The Mediterranean climate of California, with wet winters and dry summers, produces a sediment layer we can pull apart like pages in a book," said U-M paleoceanographer and study co-author Ingrid Hendy. "Although these sediments have been studied before, we are using new technology to examine them in unprecedented detail." Hendy and members of her lab collected the California sediments in 2009 using a coring device that allowed them to sample large portions of the sea floor beneath the Santa Barbara Channel. Hendy is an associate professor in the U-M Department of Earth and Environmental Sciences. In the lab, fish scales from the core were identified under a binocular dissecting microscope by comparing them to reference specimens from the U-M Museum of Zoology collection. Anchovies in the collection were bought at the San Pedro Fish Market, near Long Beach, Calif., in 1922. The sardines came from Barkley Sound, on the west coast of Vancouver Island, and were collected in 1933. The fish-scale analysis was performed by former U-M undergraduate Alexandra Skrivanek, who is now a graduate student at the University of Florida. Hendy's lab has also helped to advance techniques used to date the layers within marine sediment cores. Those advances involve improved radiocarbon dating of organic materials in the sediments and better ways to count the annual layers, Hendy said. The scientists described a collapse as a drop below 10 percent of the average peak in fish populations, as estimated from the paleorecord. Anchovy took an average of eight years to recover from a collapse, while sardine and hake took an average of 22 years. The record also showed that sardine and anchovy fluctuated synchronously over the 500-year study period. Combined collapses may compound the impact on predators and the fishery, the scientists said. The finding runs counter to suggestions that the two species' cycles alternate. Sardine and anchovy have at times been the most heavily harvested fish off Southern California in terms of volume. Hake, also known as Pacific whiting, spawn off California but are harvested in large volumes off the Pacific Northwest and Canada. The new study concludes these forage fish are well-suited to variable fishing rates that target the species in times of abundance, "while recognizing that mean persistence of fishable populations is one to two decades, and that switching to other target species will become a necessity." Collapses last, on average, "too long for the industry to simply wait out the return of the forage fish." The study authors concluded that "well-designed reserve thresholds" and adjustable harvest rates help protect the forage species, the fishery and nonhuman predators for the long term. However, they added that "reserve thresholds only protect the seed stock for recovery, and cannot prevent collapses from occurring." More information: S. McClatchie et al. Collapse and recovery of forage fish populations prior to commercial exploitation, Geophysical Research Letters (2017). DOI: 10.1002/2016GL071751


Squires D.,Southwest Fisheries Science Center
Fish and Fisheries | Year: 2010

Buybacks of fishing vessels, licences, access and other rights, and gear, sometimes called decommissioning schemes, have traditionally been a key policy tool to address overcapacity, overexploitation of fish stocks, and distributional issues in fisheries. Two more issues can be added, sustainable use of ecosystems and conservation of biodiversity (i.e. ecological public goods and services) and providing a transition to a more rationalized fishery. This study discusses reasons for buybacks; examines consequences; considers asymmetric information, design of buyback auctions and other design issues; buybacks as a transition to a rationalized industry with strong property rights and governance, financing and transnational fisheries; draws out key lessons from the international experience; and provides an overall evaluation. © 2010 Blackwell Publishing Ltd.


Wilson C.,Southwest Fisheries Science Center
Geophysical Research Letters | Year: 2011

The dissipation of surface tidal energy into internal tides plays a critical role in ocean mixing. However, quantifying the spatial distribution of this energy flux, which is required for ocean and climate modeling, has been largely based on modeling efforts and there is a need for validating observations. The summer development of large blooms of chlorophyll along 30N in the E. Pacific is presented as evidence of enhanced tidal mixing. The region near 30 is a "double" critical latitude, with a transformation of internal waves occurring at both diurnal and semidiurnal frequencies. The breakdown at the critical latitude of internal waves generated at Hawaii could provide the physical mechanism to explain these blooms. The blooms develop in a region characterized by a weak summer surface stratification, which is therefore more susceptible to mixing. Copyright 2011 by the American Geophysical Union.


MacFarlane R.B.,Southwest Fisheries Science Center
Canadian Journal of Fisheries and Aquatic Sciences | Year: 2010

The greatest rates of energy accumulation and growth in subyearling Chinook salmon (Oncorhynchus tshawytscha) occurred during the first month following ocean entry, supporting the importance of this critical period. Data from an 11-year study in the coastal ocean off California and the San Francisco Estuary revealed that juvenile salmon gained 3.2 kj·day-1 and 0.8 g·day-1, representing 4.3%·day-1 and 5.2% day-1, respectively, relative to estuary exit values. Little gain in energy (0.28 kj·day-1) or size (0.07 g·day-1) occurred in the estuary, indicating that the nursery function typically ascribed to estuaries can be deferred to initial ocean residence. Calculated northern anchovies (Engraulis mordax) equivalents to meet energy gains were one anchovy per day in the estuary (8% body weight·day-1) and about three per day immediately following ocean entry (15% body weight·day-1). Energy content in the estuary was positively related to higher salinity and lower freshwater outflow, whereas in the ocean, cooler temperatures, lower sea level, and greater upwelling resulted in greater gains. These results suggest that greater freshwater flows, warmer sea temperatures, and reduced or delayed upwelling, all of which are indicated by some (but not all) climate models, will likely decrease growth of juvenile Chinook salmon, leading to reduced survival.


Wegner N.C.,Southwest Fisheries Science Center | Snodgrass O.E.,Southwest Fisheries Science Center | Dewar H.,Southwest Fisheries Science Center | Hyde J.R.,Southwest Fisheries Science Center
Science | Year: 2015

Endothermy (the metabolic production and retention of heat to warm body temperature above ambient) enhances physiological function, and whole-body endothermy generally sets mammals and birds apart from other animals. Here, we describe a whole-body form of endothermy in a fish, the opah (Lampris guttatus), that produces heat through the constant "flapping" of wing-like pectoral fins and minimizes heat loss through a series of counter-current heat exchangers within its gills. Unlike other fish, opah distribute warmed blood throughout the body, including to the heart, enhancing physiological performance and buffering internal organ function while foraging in the cold, nutrient-rich waters below the ocean thermocline. © 2015 by the American Association for the Advancement of Science; all rights reserved.


McClatchie S.,Southwest Fisheries Science Center
Geophysical Research Letters | Year: 2012

Pacific sardines (Sardinops sagax) fluctuate widely in abundance over interannual to multidecadal time scales. For Pacific sardines, there have been repeated attempts to link fluctuations in biomass to indices of climatic variability, such as the Pacific Decadal Oscillation (PDO). Correlations between the PDO with periods of 40-76 years, and sardine biomass with periods of 40-70 years, have been inferred using 90-year time series (e.g. 1920-2010). The inferred correlations cannot be tested because the long-period fluctuations are outside the observation window that can be analysed statistically, i.e. the period (40-76 years) is greater than half the length of the series (45 years). To date, there has been no attempt to test the relationship between lowfrequency fluctuations of sardine biomass and the PDO using longer paleoclimatic time series proxies for sardine biomass and the PDO. Here we use a 370-year record of paleoclimatic proxies to show that fluctuations in sardine biomass off California are not related to the PDO, despite the appearance of correlation in the 90-year record from 1920 to the present day. © 2012. American Geophysical Union.


Gerrodette T.,Southwest Fisheries Science Center
Marine Ecology | Year: 2011

Despite more than half a century of criticism, significance testing continues to be used commonly by ecologists. Significance tests are widely misused and misunderstood, and even when properly used, they are not very informative for most ecological data. Problems of misuse and misinterpretation include: (i) invalid logic; (ii) rote use; (iii) equating statistical significance with biological importance; (iv) regarding the P-value as the probability that the null hypothesis is true; (v) regarding the P-value as a measure of effect size; and (vi) regarding the P-value as a measure of evidence. Significance tests are poorly suited for inference because they pose the wrong question. In addition, most null hypotheses in ecology are point hypotheses already known to be false, so whether they are rejected or not provides little additional understanding. Ecological data rarely fit the controlled experimental setting for which significance tests were developed. More satisfactory methods of inference assess the degree of support which data provide for hypotheses, measured in terms of information theory (model-based inference), likelihood ratios (likelihood inference) or probability (Bayesian inference). Modern statistical methods allow multiple data sets to be combined into a single likelihood framework, avoiding the loss of information that can occur when data are analyzed in separate steps. Inference based on significance testing is compared with model-based, likelihood and Bayesian inference using data on an endangered porpoise, Phocoena sinus. All of the alternatives lead to greater understanding and improved inference than provided by a P-value and the associated statement of statistical significance. Published 2011.

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