Acoustic characteristics of forage fish species in the Gulf of Alaska and Bering Sea based on Kirchhoff-approximation models
01 Oct 2004-Canadian Journal of Fisheries and Aquatic Sciences (NRC Research Press Ottawa, Canada)-Vol. 61, Iss: 10, pp 1839-1850
TL;DR: KRM backscatter models were used to quantify acoustic characteristics of Bering Sea and Gulf of Alaska pelagic fish species and species could be separated in two major groups: fish with gas-filled swimbladders and fish without Swimbladders.
Abstract: Acoustic surveys are routinely used to assess fish abundance. To ensure accurate population estimates, the characteristics of echoes from constituent species must be quantified. Kirchhoff-ray mode ...
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TL;DR: It is found that: (1) time of day was the most important factor in predicting whether a whale was feeding when it surfaced; and (2) surface feeding occurred more often around more dense, vertically distributed schools of prey.
Abstract: Analyses of the foraging behavior of large cetaceans have generally focused on either correlations with environmental conditions at regional scales or observations of surface behavior. We employed a novel approach combining multi-scale analyses of simultaneous environmental condi- tions, surface and subsurface humpback whale Megaptera novaeangliae movements, and sand lance Ammodytes spp. prey aggregations in the Gulf of Maine, USA. At the fine scale (<1 km), digital tags recorded whale movement and behavior in 3 dimensions. Concurrent synoptic prey data were col- lected using EK60 echosounders with simultaneous surface measurements of temperature and rela- tive fluorescence within 1 km of the tagged whale. A geospatial analysis of environmental features and foraging patterns was conducted at the regional, seascape scale (~10 km). At the seascape scale, we found: (1) a negative relationship between relative fluorescence and sand lance density; (2) a pos- itive relationship between predator surface feeding, presumed sand lance density, and sand bottom types near high-slope edges; (3) a cyclical relationship for predator surface-feeding likelihood and prey density with tidal height; and (4) an observed temporal lag between peak prey density and predator surface-feeding likelihood. At the fine scale, we found that: (1) time of day was the most important factor in predicting whether a whale was feeding when it surfaced; and (2) surface feeding occurred more often around more dense, vertically distributed schools of prey. Multiscale and multi- trophic level studies are an important component in understanding the foraging ecology of top preda- tors in marine systems.
126 citations
Cites methods from "Acoustic characteristics of forage ..."
...In addition to visual identification, we compared the data at 120 and 38 kHz to categorize acoustic targets and schools as non-swimbladdered fish (e.g. sand lance) due to frequency-dependent scattering (Freeman et al. 2004, Gauthier & Horne 2004)....
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TL;DR: The ability of parents to adjust their foraging time by more than 2 h/d explains why they were able to maintain chick-feeding rates of more than 3.5 meals/d across a 10-fold range in local food density.
Abstract: Flexible time budgets allow individual animals to buffer the effects of variable food availability by allocating more time to foraging when food density decreases. This trait should be especially important for marine predators that forage on patchy and ephemeral food resources. We examined flexible time allocation by a long-lived marine predator, the Common Murre (Uria aalge), using data collected in a five-year study at three colonies in Alaska (USA) with contrasting environmental conditions. Annual hydroacoustic surveys revealed an order-of-magnitude variation in food density among the 15 colony-years of study. We used data on parental time budgets and local prey density to test predictions from two hypotheses: Hypothesis A, the colony attendance of seabirds varies nonlinearly with food density; and Hypothesis B, flexible time allocation of parent murres buffers chicks against variable food availability. Hypothesis A was supported; colony attendance by murres was positively correlated with food over a limited range of poor-to-moderate food densities, but independent of food over a broader range of higher densities. This is the first empirical evidence for a nonlinear response of a marine predator's time budget to changes in prey density. Predictions from Hypothesis B were largely supported: (1) chick-feeding rates were fairly constant over a wide range of densities and only dropped below 3.5 meals per day at the low end of prey density, and (2) there was a nonlinear relationship between chick-feeding rates and time spent at the colony, with chick-feeding rates only declining after time at the colony by the nonbrooding parent was reduced to a minimum. The ability of parents to adjust their foraging time by more than 2 h/d explains why they were able to maintain chick-feeding rates of more than 3.5 meals/d across a 10-fold range in local food density.
107 citations
Additional excerpts
...…centimeters): walleye pollock (Theragra chalcogramma) TS ¼ 21.1 log(L) 70.5; herring TS ¼ 202.0 log(L) 67.6; and capelin TS¼ 28.4 log(L) 81.8 (all from Gauthier and Horne 2004); sand lance TS ¼ 20.0 log(L) 80 (Thomas et al. 2002); and Pacific cod (Gadus macrocephalus) TS¼ 20.0 log(L) 65 (Rose…...
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TL;DR: The location and diving behavior of tagged whales suggested that whales were favoring capelin over pollock as a prey source.
Abstract: Tags containing acoustic time-depth transmitters (ATDT) were attached to four humpback whales near Kodiak, Alaska. Tags allowed for whale dive depths to be recorded in real time. Acoustic and mid-water trawl surveys were conducted concurrent with tagging efforts within the study area to quantify available fish resources and describe potential prey selection by humpback whales. Recorded dives were grouped through visual assessment and t-tests. Dives that indicated likely foraging occurred at a mean maximum depth of 106.2 m with 62% of dives occurring between 92 m and 120 m. Acoustic backscatter from fish surveys was attributed to potential humpback prey based on known target strength values and 10 net tows. Capelin comprised 84% of the total potential prey abundance in the region followed by age 0 (12%) and juvenile pollock (2%), and eulachon (<1%). Although horizontally segregated in the region, both capelin and age 0 pollock were distributed at depths exceeding 92 m with maximum abundance between 107 m and 120 m. The four-tagged humpbacks were found to forage in areas with greatest capelin densities but bypassed areas of high age 0 pollock abundance. The location and diving behavior of tagged whales suggested that whales were favoring capelin over pollock as a prey source.
57 citations
TL;DR: In this article, the authors used acoustic and trawl data from a non-target survey to evaluate distributions of capelin ( Mallotus villosus), age-0 Pacific cod ( Gadus macrocephalus ), and age- 0 walleye pollock ( Theragra chalcogramma, herein pollock) in the eastern Bering Sea.
Abstract: Juvenile and small adult fish, typically called forage fish, are an important but poorly studied part of the eastern Bering Sea (EBS) ecosystem Acoustic and trawl data from a non-target survey were used to evaluate distributions of capelin ( Mallotus villosus ), age-0 Pacific cod ( Gadus macrocephalus ), and age-0 walleye pollock ( Theragra chalcogramma , herein pollock) in 2006–2010 Within the surface zone (15 m to ~35 m, evaluated 2006–2010), capelin occurred throughout the EBS but primarily in the middle shelf Capelin were also present in the midwater zone (~35 m to 05 m off-bottom) in both 2009 and 2010 (evaluated 2009–2010), and resulted in water column zone (15 m to 05 m off-bottom) distributions that differed from surface zone characterizations Age-0 Pacific cod occurred primarily in the surface zone of the middle and outer shelf regions in all years As midwater and surface zone age-0 Pacific cod were often coincident, water column zone distributions in 2009–2010 were similar to surface zone distributions Age-0 pollock were found in the EBS surface zone in all years, primarily in the middle and outer shelf regions High densities of age-0 pollock occurred in the midwater zone in 2006–2007 and 2009–2010 Water column zone distributions of age-0 pollock were similar to surface zone distributions in 2006–2007, but differed in 2009–2010 due to low numbers of age-0 pollock in the surface zone and presence of high densities in the midwater zone of the outer shelf region While general patterns in capelin distribution in the surface zone were similar between the present and the previous studies, the acoustic–trawl characterization suggested that capelin densities were high in the middle shelf region As expected, surface zone distributions of age-0 Pacific cod and age-0 pollock were similar to previous characterizations Observed high densities of midwater age-0 pollock have not been described by previous studies Annual abundance indices based on bottom or surface trawl data alone will not be sufficient in all years Data and conclusions from non-target surveys may be constrained compared to dedicated survey efforts, but can provide baseline distributions, potential abundance indices, and insight for planning future research
39 citations
TL;DR: Changes in swimbladder morphology in an Atlantic herring Clupea harengus with pressure were examined by magnetic resonance imaging of a dead fish in a purpose-built pressure chamber and uneven compression has a reduced effect on acoustic backscattering than symmetrical compression.
Abstract: Changes in swimbladder morphology in an Atlantic herring Clupea harengus with pressure were examined by magnetic resonance imaging of a dead fish in a purpose-built pressure chamber. Swimbladder volume changed with pressure according to Boyle’s Law, but compression in the lateral aspect was greater than in the dorsal aspect. This uneven compression has a reduced effect on acoustic backscattering than symmetrical compression and would elicit less pronounced effects of depth on acoustic biomass estimates of C. harengus.
34 citations
Cites methods from "Acoustic characteristics of forage ..."
...Radiographic techniques have been used extensively to extract shapes of swimbladders for use in acoustic backscattering models (Clay & Horne, 1994; Horne & Jech, 1999; Hazen & Horne, 2003; Gauthier & Horne, 2004; Reeder et al., 2004)....
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References
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DOI•
01 Jan 1983
TL;DR: In this article, the APSO Joint Panel on Oceanographic Tables and Standards (APSO) and SCOR Working Group (SCOR) have published a joint report on oceanographic tables and standards.
Abstract: Endorsed by
Unesco/SCOR/ICES/lAPSO Joint Panel
on Oceanographic Tables and Standards
and SCOR Working Group 51
1,534 citations
TL;DR: In this paper, a simple nine-term, eight-variable sound speed equation for sound speed in the oceans is presented, suitable for programmable pocket calculators, and ranges of validity encompass: temperature −2° to 30° C, salinity 30° to 40°/°°°, and depth 0 to 8000 m.
Abstract: A simple yet accurate nine‐term, eight‐variable equation for sound speed in the oceans, suitable for programmable pocket calculators, is presented. Ranges of validity encompass: temperature −2° to 30° C, salinity 30° to 40°/°°, and depth 0 to 8000 m. Good quality oceanographic data at 15 worldwide stations, including two in the Mediterranean, were utilized for the computations. The Del Grosso and Mader [J. Acoust. Soc. Am. 52, 961–974 (1972)] sound‐speed equation was employed as ’’truth’’ after comparisons among Wilson [J. Acoust. Soc. Am. 32, 641–644. 1357 (1960)] and others. A precise method of computing pressure is detailed. Practical differences in critical depth, excess depth, conjugate depth, deep sound‐speed gradients, and echo‐sounder corrections are shown to be small between computations based on Wilson or Del Grosso and Mader sound‐speed equations.
577 citations
"Acoustic characteristics of forage ..." refers background in this paper
...Density and sound speed of water are easily calculated using ambient temperature, salinity, and depth (e.g., Mackenzie 1981; UNESCO 1983)....
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TL;DR: The data collected in Alaska are consistent with the hypothesis that Steller sea lions in the declining regions were nutritionally compromised because of the relative quality of prey available to them, rather thanBecause of the overall quantity of fish per se (acute nutritional stress).
Abstract: The decline of Steller sea lions Eumetopias jubatus in the Gulf of Alaska and Aleutian Islands between the late 1970s and 1990s may have been related to reduced availability of suitable prey. Many studies have shown that pinnipeds and other mammals suffering from nutritional stress typically exhibit reduced body size, reduced productivity, high mortality of pups and juveniles, altered blood chemistry and specific behavioural modifications. 2. Morphometric measurements of Steller sea lions through the 1970s and 1980s in Alaska indicate reduced body size. Reduced numbers of pups born and an apparent increase in juvenile mortality rates also appear to be nutritionally based. Blood chemistry analyses have further shown that Steller sea lions in the Gulf of Alaska and Aleutian Islands area exhibited signs of an acute phase reaction, or immune reaction, in response to unidentified physical and/or environmental stress. Behavioural studies during the 1990s have not noted any changes that are indicative of an overall shortage in the quantity of prey available to lactating female sea lions. 3. The data collected in Alaska are consistent with the hypothesis that Steller sea lions in the declining regions were nutritionally compromised because of the relative quality of prey available to them (chronic nutritional stress), rather than because of the overall quantity of fish per se (acute nutritional stress). This is further supported by captive studies that indicate the overall quality of prey that has been available to Steller sea lions in the declining popu- lation could compromise the health of Steller sea lions and hinder their recovery.
350 citations
"Acoustic characteristics of forage ..." refers background in this paper
...It has been hypothesized that changes in the composition, distribution, and availability of fish in Steller sea lion habitat are in part responsible for their decline and lack of recovery (Rosen and Trites 2000; Stickney 2000; Trites and Donnelly 2003)....
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TL;DR: In this article, the relative swimbladder contribution to both maximum and averaged dorsal aspect backscattering cross sections is shown to be approximately 90% to 95%, which is higher than most other estimates.
Abstract: Previous determinations of the swimbladder contribution to the fish backscattering cross section have been hindered by ignorance of the acoustic boundary conditions at the swimbladder wall. The present study circumvents this problem by direct comparison of target strengths of three gadoid species and mackerel — anatomically comparable fusiform fish which respectively possess and lack a swimbladder. The relative swimbladder contribution to both maximum and averaged dorsal aspect backscattering cross sections is shown to be approximately 90% to 95%, which is higher than most other estimates. The new results were established for fish of 29‐ to 42‐cm length and acoustic frequencies of 38 and 120 kHz.
333 citations
"Acoustic characteristics of forage ..." refers background in this paper
...In addition to physical characteristics such as frequency (Foote 1982), TS depends on fish size (Nakken and Olsen 1977), anatomical features (e.g., presence of a swimbladder; Foote 1980a), morphology (e....
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...…such as frequency (Foote 1982), TS depends on fish size (Nakken and Olsen 1977), anatomical features (e.g., presence of a swimbladder; Foote 1980a), morphology (e.g., swimbladder shape; McClatchie et al. 1996a), and physiological state (e.g., gonadal maturation and gut fullness; Ona…...
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...Because of the large density and sound speed contrasts of gas and water, the echo intensity of a fish primarily depends on the presence or absence of a gas-filled swimbladder (Haslett 1962; Foote 1980a)....
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...Fish behavior can also significantly alter TS through changes in fish orientation relative to the wave front (Nakken and Olsen 1977; Foote 1980b; Blaxter and Blatty 1990) and vertical movement within the water column, which changes swimbladder volume (Ona 1990; Mukai and Iida 1996; Rose and Porter…...
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TL;DR: Evidence for both periodic variations, as from uncompensated vertical migrations, and seasonal variations, caused by the fat cycle and gonad development, are presented.
Abstract: The swimbladder is recognized as responsible for a major part of the acoustic backscattering from fish. In most fishes it has the function of a buoyancy regulator but in others its main function is rather unclear. Based on methods for exact mapping of the swimbladder shape, observations of deviations from normal appearance and shape are discussed in relation to possible effects on target strength. Evidence for both periodic variations, as from uncompensated vertical migrations, and seasonal variations, caused by the fat cycle and gonad development, are presented.
257 citations
"Acoustic characteristics of forage ..." refers background in this paper
...Fish behavior can also significantly alter TS through changes in fish orientation relative to the wave front (Nakken and Olsen 1977; Foote 1980b; Blaxter and Blatty 1990) and vertical movement within the water column, which changes swimbladder volume (Ona 1990; Mukai and Iida 1996; Rose and Porter 1996)....
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...…can also significantly alter TS through changes in fish orientation relative to the wave front (Nakken and Olsen 1977; Foote 1980b; Blaxter and Blatty 1990) and vertical movement within the water column, which changes swimbladder volume (Ona 1990; Mukai and Iida 1996; Rose and Porter 1996)....
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...…such as frequency (Foote 1982), TS depends on fish size (Nakken and Olsen 1977), anatomical features (e.g., presence of a swimbladder; Foote 1980a), morphology (e.g., swimbladder shape; McClatchie et al. 1996a), and physiological state (e.g., gonadal maturation and gut fullness; Ona 1990)....
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