scholarly journals Simulating the effects of side-aspect fish orientation on acoustic biomass estimates

2009 ◽  
Vol 66 (6) ◽  
pp. 1398-1403 ◽  
Author(s):  
Kevin M. Boswell ◽  
Brian M. Roth ◽  
James H. Cowan
Keyword(s):  
Simulated Data ◽  
Population Level ◽  
Target Strength ◽  
Fish Length ◽  
Fish Biomass ◽  
Simulation Methods ◽  
Acoustic Data ◽  
Age Class ◽  
Brevoortia Patronus ◽  
Systematic Manipulation

Abstract Boswell, K. M., Roth, B. M., and Cowan, Jr J. H. 2009. Simulating the effects of side-aspect fish orientation on acoustic biomass estimates. – ICES Journal of Marine Science, 66: 1398–1403. Simulation methods were used to investigate the effect of side-aspect fish orientation on estimates of fish biomass derived from acoustic data. Three population-level length distributions (n = 1000 individuals) were simulated (identical, uniform, and age class) and applied to a target strength (TS) function of fish length previously derived for Gulf menhaden (Brevoortia patronus). Systematic manipulation of the TS–length coefficients strongly affected the biomass estimates. Based on simulations, biomass estimates decreased markedly from the true side-aspect to head- or tail-on orientation, with estimates of population biomass decreasing by 80% when orientation deviated by as little as 30° from true side-aspect. Simulated data indicate that biomass estimates generated from surveys may be grossly inaccurate if fish orientation is not taken into account.

Evaluation of target strength–fish length equation choices for estimating estuarine fish biomass

Hydrobiologia ◽  
2008 ◽  
Vol 610 (1) ◽  
pp. 113-123 ◽  
Author(s):  
Kevin M. Boswell ◽  
Michael D. Kaller ◽  
James H. Cowan ◽  
Charles A. Wilson
Keyword(s):  
Target Strength ◽  
Estuarine Fish ◽  
Fish Length ◽  
Fish Biomass

scholarly journals A Bayesian approach to estimating target strength

2009 ◽  
Vol 66 (6) ◽  
pp. 1197-1204 ◽  
Author(s):  
Sascha M. M. Fässler ◽  
Andrew S. Brierley ◽  
Paul G. Fernandes
Keyword(s):  
Bayesian Approach ◽  
Tilt Angle ◽  
Clupea Harengus ◽  
Target Strength ◽  
Model Parameters ◽  
Fish Length ◽  
Acoustic Data ◽  
Abundance Estimates ◽  
The Mean ◽  
Conventional Models

Abstract Fässler, S. M. M., Brierley, A. S., and Fernandes, P. G. 2009. A Bayesian approach to estimating target strength. – ICES Journal of Marine Science, 66: 1197–1204. Currently, conventional models of target strength (TS) vs. fish length, based on empirical measurements, are used to estimate fish density from integrated acoustic data. These models estimate a mean TS, averaged over variables that modulate fish TS (tilt angle, physiology, and morphology); they do not include information about the uncertainty of the mean TS, which could be propagated through to estimates of fish abundance. We use Bayesian methods, together with theoretical TS models and in situ TS data, to determine the uncertainty in TS estimates of Atlantic herring (Clupea harengus). Priors for model parameters (surface swimbladder volume, tilt angle, and s.d. of the mean TS) were used to estimate posterior parameter distributions and subsequently build a probabilistic TS model. The sensitivity of herring abundance estimates to variation in the Bayesian TS model was also evaluated. The abundance of North Sea herring from the area covered by the Scottish acoustic survey component was estimated using both the conventional TS–length formula (5.34×109 fish) and the Bayesian TS model (mean = 3.17×109 fish): this difference was probably because of the particular scattering model employed and the data used in the Bayesian model. The study demonstrates the relative importance of potential bias and precision of TS estimation and how the latter can be so much less important than the former.

scholarly journals Application of in situ target-strength estimations in lakes: examples from rainbow-smelt surveys in Lakes Erie and Champlain

2003 ◽  
Vol 60 (3) ◽  
pp. 500-507 ◽  
Author(s):  
L.G Rudstam ◽  
S.L Parker ◽  
D.W Einhouse ◽  
L.D Witzel ◽  
D.M Warner ◽  
...  
Keyword(s):  
Lake Erie ◽  
Growing Season ◽  
Target Strength ◽  
Fish Length ◽  
Osmerus Mordax ◽  
Rainbow Smelt ◽  
Acoustic Data ◽  
Size Groups ◽  
High Fish

Abstract Acoustic abundance of fish depends directly on the target strength (TS) of the fish surveyed. We analyzed 70 and 120 kHz acoustic data from two lakes with abundant rainbow-smelt (Osmerus mordax) populations. Using repeated surveys through the summer growing season, we derived a relationship between TS (dB) and fish length L (cm) at 120 kHz (TS = 19.9 log10 L − 67.8). Values for 70 kHz were similar. In situ TS increased with fish density, indicating a bias from accepting multiple targets at high fish densities. Correcting for this bias increased estimates of smelt abundance by up to 18% in Lake Erie and up to 100% in Lake Champlain. Multiple modes in the TS distributions observed for older fish do not reflect different size groups, as the same modes can be observed from measurements from a single fish. Smelt released gas bubbles during the evening ascent, and these bubbles had TS (−60 to −58 dB) within the range of TS observed from the fish. Gas-bubble release occurred mostly during the migration. Conducting surveys after the ascent is completed will decrease bias associated with counting bubbles as fish.

scholarly journals Response of Prochilodus nigricans to flood pulse variation in the central Amazon

2018 ◽  
Vol 5 (6) ◽  
pp. 172232 ◽  
Author(s):  
Peter B. Bayley ◽  
Leandro Castello ◽  
Vandick S. Batista ◽  
Nidia N. Fabré
Keyword(s):  
Population Size ◽  
Flood Pulse ◽  
Fish Length ◽  
Age Class ◽  
Annual Population ◽  
Feeding Habitat ◽  
Age Structured ◽  
Lag Times ◽  
Floodplain Habitats ◽  
Pulse Variation

The influence of the flood pulse on fish populations has been posited, but infrequently tested or quantified. Here, we tested the effect of habitat on population size, using Prochilodus nigricans as a case study species. Floodplain habitat was based on the littoral zone area occupied by P. nigricans to feed. The magnitude of this habitat in each hydrological year, the moving littoral (ML), was expressed as the sum of daily littoral areas during the advancing flood pulse, using satellite-based passive microwave data. Annual population size was estimated by age class, using a dynamic age-structured model (MULTIFAN-CL) based on catches, effort and fish length frequencies from the Manaus-based fishery over 12.75 years. The principal null hypothesis was that the ML, using three lag times, had no effect on population size of a single age class of P. nigricans . The population size at 29 months of age was positively related ( p  = 0.00030) to floodplain habitat (ML) earlier in the same year, when the fish were 21–27 months old. The result implies a density-dependent relationship for the population with respect to its feeding habitat. Potential mechanisms governed by flood pulse variation and habitat quality for this and other species using floodplain habitats are discussed.

scholarly journals Target Strength and swimbladder morphology of Mueller’s pearlside (Maurolicus muelleri)

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
B. Sobradillo ◽  
G. Boyra ◽  
U. Martinez ◽  
P. Carrera ◽  
M. Peña ◽  
...  
Keyword(s):  
Relevant Information ◽  
Target Strength ◽  
Fish Length ◽  
Mesopelagic Fish ◽  
Bay Of Biscay ◽  
Numerical Abundance ◽  
Density Filter ◽  
Pressure Changes ◽  
First Time ◽  
Best Fit

AbstractIn the last few years, there has been increasing interest in the commercial exploitation of mesopelagic fish and a trawl-acoustic methodology has been recommended to make estimates of abundance of these resources. This study provides relevant information on the scattering properties of a key mesopelagic fish species in the Bay of Biscay, Mueller’s pearlside (Maurolicus muelleri), necessary to convert the acoustic density into numerical abundance. The target strength (TS) of pearlside was estimated for the first time at five frequencies commonly used in acoustic surveys. A high-density filter was applied to reduce the bias derived from overlapping echoes erroneously assigned to single targets. Its relationship with fish length (b20) was also determined (−65.9 ± 2, −69.2 ± 3, −69.2 ± 2, −69.5 ± 2.5 and −71.5 ± 2.5 dB at 18, 38, 70, 120 and 200 kHz, respectively). Biomass estimates of pearlside in the Bay of Biscay during the four years of study (2014–2017) are given using the 38 kHz frequency. Morphological measurements of the swimbladder were obtained from soft X-ray images and used in the backscattering simulation of a gas-filled ellipsoid. Pearlside is a physoclist species, which means that they can compensate the swimbadder volume against pressure changes. However, the best fit between the model and the experimental data showed that they lose that capacity during the trawling process, when the swimbladder volume is affected by Boyle’s law.

scholarly journals Comparing the modelled and measured target-strength variability of walleye pollock, Theragra chalcogramma

2004 ◽  
Vol 61 (3) ◽  
pp. 363-377 ◽  
Author(s):  
Elliott L. Hazen ◽  
John K. Horne
Keyword(s):  
Ex Situ ◽  
Target Strength ◽  
Physical Factors ◽  
Fish Length ◽  
Acoustic Frequency ◽  
Backscatter Intensity ◽  
Model Predictions ◽  
Strength Variability ◽  
Boyle’S Law ◽  
Insight Into

Abstract Many biological and physical factors potentially affect target strength. While these sources have been identified, few studies have compared the relative effects of individual factors. Modelled and measured target strengths in non-dimensional metrics were used to compare and rank the effects of fish length, tilt, depth, and acoustic frequency on backscatter intensity. Ex situ measurements of target strength were used to examine the effects of tilt and depth and then compared to backscatter model predictions. Swimbladder volume reduction due to increasing pressure at depth was modelled using Boyle's law and by varying the ratio of dorsal to lateral compression. We found that length has the largest effect on the modelled and measured backscatter intensity, followed by tilt, frequency, and depth. Including tilt distributions in backscatter estimates improved the match between empirical target-strength measures and model predictions. Non-dimensional influence ratios provide insight into the sources and magnitudes of the backscatter variability.

Estimation of Fish Length from Acoustic Target Strengths

1987 ◽  
Vol 44 (10) ◽  
pp. 1782-1785 ◽  
Author(s):  
U. Buerkle
Keyword(s):  
Gadus Morhua ◽  
Statistical Significance ◽  
Orientation Distribution ◽  
Target Strength ◽  
Fish Length ◽  
Fish Sample ◽  
Length Frequency ◽  
Frequency Structure ◽  
Acoustic Target

I show that fish length distributions calculated from acoustic target strengths of cod (Gadus morhua) are in error when target strength–length relationships are used that do not account for the orientation distribution of the fish. The magnitude and statistical significance of the errors vary with the length frequency structure of the fish sample and are thought to be large enough to question the value of acoustically determined lengths in fish surveys if corrections for fish orientation are not applied.

Factors influencing coastal cutthroat trout (Oncorhynchus clarkii clarkii) seasonal survival rates: a spatially continuous approach within stream networks

2009 ◽  
Vol 66 (4) ◽  
pp. 613-632 ◽  
Author(s):  
Aaron M. Berger ◽  
Robert E. Gresswell
Keyword(s):  
Survival Rates ◽  
Fork Length ◽  
Cutthroat Trout ◽  
Population Level ◽  
Fish Length ◽  
Watershed Scale ◽  
Stream Networks ◽  
Oncorhynchus Clarkii ◽  
Discharge Temperature ◽  
Coastal Cutthroat Trout

Mark–recapture methods were used to examine watershed-scale survival of coastal cutthroat trout ( Oncorhynchus clarkii clarkii ) from two headwater stream networks. A total of 1725 individuals (≥100 mm, fork length) were individually marked and monitored seasonally over a 3-year period. Differences in survival were compared among spatial (stream segment, subwatershed, and watershed) and temporal (season and year) analytical scales, and the effects of abiotic (discharge, temperature, and cover) and biotic (length, growth, condition, density, movement, and relative fish abundance) factors were evaluated. Seasonal survival was consistently lowest and least variable (years combined) during autumn (16 September – 15 December), and evidence suggested that survival was negatively associated with periods of low stream discharge. In addition, relatively low (–) and high (+) water temperatures, fish length (–), and boulder cover (+) were weakly associated with survival. Seasonal abiotic conditions affected the adult cutthroat trout population in these watersheds, and low-discharge periods (e.g., autumn) were annual survival bottlenecks. Results emphasize the importance of watershed-scale processes to the understanding of population-level survival.

scholarly journals Measuring herring densities with one real and several phantom research vessels

2009 ◽  
Vol 66 (6) ◽  
pp. 1264-1269 ◽  
Author(s):  
Ruben Patel ◽  
Egil Ona
Keyword(s):  
Pelagic Fish ◽  
Target Strength ◽  
Fish Biomass ◽  
Marine Science ◽  
Lateral Aspect ◽  
Multibeam Sonar ◽  
The Real ◽  
Backscattering Strength ◽  
The Mean

Abstract Patel, R., and Ona, E. 2009. Measuring herring densities with one real and several phantom research vessels. – ICES Journal of Marine Science 66: 1264–1269. Vessel-induced avoidance can potentially cause a large bias in acoustic estimates of schooling, pelagic-fish biomass. This paper presents a method for quantifying this uncertainty. Volume-backscattering strength (Sv) from a horizontally projecting, multibeam sonar (Simrad MS70) is resampled to form synthetic, vertical, echosounder beams to the side of the survey vessel. These data are analysed as if they were collected from phantom vessels surveying parallel transects at fixed ranges from the real vessel. The nautical-area-backscattering coefficients (sA) from the synthetic echograms are compared with those measured by conventional 70 and 120 kHz echosounders (Simrad EK60) on the real vessel. Data collected in 2006 from schools of Norwegian spring-spawning herring are used to illustrate the method and explore its limitations. Potential effects of vessel-induced avoidance are evaluated by comparing the mean sA values observed from the phantom vessels with those observed from the real vessel. The technique also allows direct estimates of the mean lateral-aspect target strength of in situ herring.

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