Analysis of Spanish acoustic surveys for sardine, 1991–1993: abundance estimates and inter-annual variability

Abstract:Animals often select for habitats that increase their chance of survival by balancing the need to acquire food, reproduce and avoid predation. Perennial blooms of golden jellyfish (Mastigias papua etpisoni) are present in Jellyfish Lake, Palau, a popular tourist destination. Based on the species’ economic importance and unusual behavioural complexity, increased understanding of jellyfish habitat selection is necessary. We used a novel approach, a REMUS autonomous underwater vehicle, to quantify jellyfish distribution, abundance and habitat, and compared these findings to traditional methods. Midday acoustic surveys showed jellyfish distribution was patchy and the population resided mainly on the eastern side of the lake, as it is known that jellyfish migrate eastward towards the sun. Highest vertical densities of jellyfish were at 6–7 m, potentially to mitigate UV damage or photoinhibition of their photosymbionts, suggesting a coupling exists between their vertical distribution and water properties. Abundance estimates of jellyfish were ~2.75 and ~7.1 million (~2 million excluding bell diameters <1 cm) from acoustic and net samples, suggesting the methodology employed underestimated the population's smaller size fraction and non-synoptic surveys could impact estimates due to unresolved patchiness. Our approach could investigate population dynamics, behaviour or habitat associations on fine scales.

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A multifrequency method to classify and evaluate fisheries acoustics data

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f06-126 ◽

2006 ◽

Vol 63 (10) ◽

pp. 2225-2235 ◽

Cited By ~ 47

Author(s):

J Michael Jech ◽

William L Michaels

Keyword(s):

Clupea Harengus ◽

Biological Information ◽

Classification Algorithms ◽

Atlantic Herring ◽

Population Abundance ◽

Acoustic Data ◽

Video Images ◽

Abundance Estimates ◽

Fisheries Acoustics ◽

Acoustic Surveys

Acoustic surveys have been conducted on Georges Bank from 1998 to present to estimate Atlantic herring (Clupea harengus) population abundance. Acoustic data were collected with a 12 or 18, 38, and 120 kHz Simrad EK500 scientific echo sounder. A pelagic trawl and underwater video images were used to collect biological information and to verify the species composition of acoustic backscatter. A multifrequency classification method was developed to improve the efficiency and accuracy of classifying species from acoustic echograms. In this method, a volume backscatter (Sv) threshold was applied equivalently to all echograms, and then a composite echogram was created based on which frequencies had Sv greater than or less than the Sv threshold. The results of this method were compared with the standard method of visually scrutinizing regions, and metrics were developed to evaluate the accuracy of classification algorithms relative to current methods, as well as to assess the effects of classification methods on population abundance estimates. In general, this method matched visually scrutinized Atlantic herring regions, but with consistent biases in classifying 38 kHz backscatter. The metrics highlighted spatial and temporal changes in the acoustic landscape, which may be indicative of intra- and inter-annual biological changes.

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Sperm whale abundance estimates from acoustic surveys of the Ionian Sea and Straits of Sicily in 2003

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315407054896 ◽

2007 ◽

Vol 87 (1) ◽

pp. 353-357 ◽

Cited By ~ 41

Author(s):

T. Lewis ◽

D. Gillespie ◽

C. Lacey ◽

J. Matthews ◽

M. Danbolt ◽

...

Keyword(s):

Sperm Whale ◽

Western Mediterranean ◽

Small Sample ◽

Line Transect ◽

Ionian Sea ◽

Sperm Whales ◽

Detection Function ◽

Abundance Estimate ◽

Abundance Estimates ◽

Acoustic Surveys

Acoustic surveys for sperm whales, using line-transect methodology, were carried out in the Ionian Sea and Straits of Sicily, Mediterranean Sea, in 2003. A total of 17 whales were detected along 3846 km of designed survey track in the Ionian Sea, and no whales along 892 km in the Straits of Sicily. This total was insufficient to estimate a detection function, so further data were obtained from quasi-random passages made elsewhere in the western Mediterranean in the same year. The encounters included several tight aggregations with inter-animal spacing less than 1 km, primarily from the western Mediterranean. Including individuals from these aggregations distorted the detection function due to the small sample sizes. No such aggregations were found during formal survey of the two areas of interest, and the aggregations were therefore excluded from detection function estimation. The resultant effective strip half-width was 10.0 km (n=40). On the assumption that g(0)=1, the resulting abundance estimates for the Ionian Sea were 62 (with 95% lognormal confidence limits of [24,165]), and 0 for the Straits of Sicily. The low abundance estimate for the Ionian Sea indicates that careful monitoring of the population is needed in the future. During passages along the Hellenic Trench, that were not part of the designed survey, several sperm whales including two aggregations were detected, suggesting that this may be a higher density area and ought to be considered as a separate stratum when designing future surveys.

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Evaluating the uncertainty of abundance estimates from acoustic surveys using geostatistical simulations

ICES Journal of Marine Science ◽

10.1093/icesjms/fsp137 ◽

2009 ◽

Vol 66 (6) ◽

pp. 1377-1383 ◽

Cited By ~ 20

Author(s):

Mathieu Woillez ◽

Jacques Rivoirard ◽

Paul G. Fernandes

Keyword(s):

Acoustic Backscatter ◽

Fish Length ◽

Total Abundance ◽

Geostatistical Model ◽

Abundance Estimates ◽

Structural Relationships ◽

Coefficients Of Variation ◽

Data Points ◽

Acoustic Surveys ◽

Survey Estimates

Abstract Woillez, M., Rivoirard, J., and Fernandes, P. G. 2009. Evaluating the uncertainty of abundance estimates from acoustic surveys using geostatistical simulations. – ICES Journal of Marine Science, 66: 1377–1383. Geostatistical simulations, which can reproduce the spatial variability of a variable, are particularly helpful in estimating the uncertainty associated with the combination of different sources of variability. Acoustic surveys offer an example of such complex situations, where different data (e.g. acoustic backscatter, fish length, and fish age) must be combined to estimate abundance and its associated uncertainty. In this paper, the uncertainty of Scottish herring acoustic-survey estimates is investigated using these techniques. A specific multivariate, geostatistical model is used to describe the structural relationships, which includes highly skewed distributions of the acoustic-backscatter data and incorporates relationships between depth, mean length, and proportions-at-age. Conditional simulations, i.e. geostatistical simulations that honour the data values known at the data points, are used to generate multiple realizations of acoustic backscatter, mean length, and proportions-at-age. These are combined to produce multiple realizations of herring density over the sampled domain. Multiple realizations of total abundance and abundance-at-age are then provided. The uncertainty is assessed using basic statistics to track the significant variations of these values over the period 1989–2005. Higher coefficients of variation (CVs) are found on average for extreme ages (ages 1, 2i, 8, and 9+); otherwise, CVs are mostly around 12% for abundance-at-age and around 10% for total abundance.

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Cluster Sampling Estimation of the Variance of Abundance Estimates Derived from Quantitative Echo Sounder Surveys

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f82-031 ◽

1982 ◽

Vol 39 (1) ◽

pp. 229-231 ◽

Cited By ~ 21

Author(s):

Neal J. Williamson

Keyword(s):

Data Analysis ◽

Confidence Intervals ◽

Serial Correlation ◽

Simulation Analysis ◽

Fish Abundance ◽

Simple Random Sample ◽

Cluster Sampling ◽

Abundance Estimates ◽

Acoustic Surveys ◽

Precision And Accuracy

Serial correlation in data collected from fisheries acoustic surveys may have an effect on the precision and accuracy of fish abundance estimates. A simple random sample approach to the data analysis yields unreliable confidence intervals for mean population density when the degree of serial correlation in the data is high. The results of a simulation analysis indicate that more reliable confidence intervals can be obtained using cluster sampling estimation techniques.Key words: acoustic surveys, fish abundance estimates, cluster sampling, serial correlation

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Bias in Hydroacoustic Estimates of Fish Abundance due to Acoustic Shadowing: Evidence from Day–Night Surveys of Vertically Migrating Fish

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f92-240 ◽

1992 ◽

Vol 49 (10) ◽

pp. 2179-2189 ◽

Cited By ~ 42

Author(s):

A. R. Appenzeller ◽

W. C. Leggett

Keyword(s):

Fish Community ◽

Acoustic Scattering ◽

Fish Abundance ◽

Diel Changes ◽

Light Levels ◽

Abundance Estimates ◽

Acoustic Quantification ◽

Acoustic Methods ◽

Acoustic Surveys ◽

Acoustic Shadowing

We investigated the hypothesis that fish schooling behavior leads to underestimation of fish abundance when assessed by acoustic methods. Current methods for acoustic quantification of fish abundance rely on the assumption that fish biomass and numerical fish abundance are linearly related to acoustic scattering under all natural fish densities. However, cage experiments as well as field observations have indicated that acoustic shadowing effects occur at very dense and large aggregations of fish. Acoustic surveys of the pelagic fish community of Lake Memphremagog, Quebec, were conducted when fish were aggregated and dispersed. These differences in aggregation were related to diel responses to light levels. We found that estimates of fish abundance, as measured by echo integration, were consistently and significantly lower when fish were aggregated in dense schools. This bias was not due to diel changes in average echo level per fish, which exhibited no relationship to diel changes in vertical and hortizontal distributions. We conclude that the reduced abundance estimates obtained when fish were aggregated resulted from acoustic shadowing. Our data suggest that this bias may be as large as 50%.

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Using paired visual and passive acoustic surveys to estimate passive acoustic detection parameters for harbor porpoise abundance estimates

The Journal of the Acoustical Society of America ◽

10.1121/1.4973415 ◽

2017 ◽

Vol 141 (1) ◽

pp. 219-230

Author(s):

Eiren K. Jacobson ◽

Karin A. Forney ◽

Jay Barlow

Keyword(s):

Acoustic Detection ◽

Harbor Porpoise ◽

Abundance Estimates ◽

Acoustic Surveys ◽

Passive Acoustic

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Depth-dependent target strength of anchovy (Engraulis japonicus) measured in situ

ICES Journal of Marine Science ◽

10.1093/icesjms/fsn055 ◽

2008 ◽

Vol 65 (6) ◽

pp. 882-888 ◽

Cited By ~ 22

Author(s):

Xianyong Zhao ◽

Yong Wang ◽

Fangqun Dai

Keyword(s):

Yellow Sea ◽

Arithmetic Mean ◽

The Yellow Sea ◽

Target Strength ◽

Engraulis Japonicus ◽

Abundance Estimates ◽

Acoustic Surveys ◽

The Mean ◽

Boyle’S Law

Abstract Zhao, X., Wang, Y., and Dai, F. 2008. Depth-dependent target strength of anchovy (Engraulis japonicus) measured in situ. – ICES Journal of Marine Science, 65: 882–888. Three sets of target strength (TS) data were collected in the southern part of the Yellow Sea using a calibrated, 38 kHz, Simrad EK500 split-beam echosounder. Midwater trawl sampling showed that >97% of the catch by number was anchovy (Engraulis japonicus), with total lengths ranging from 6 to 15 cm, and that the arithmetic-mean length and root-mean-square length were 10.6 and 10.8 cm, respectively. The mean TS of anchovy in the 10–45-m layer was estimated to be –50.9 dB, with a 95% confidence interval of (–51.0, –50.8) dB. The TS data showed, however, a clear depth-dependence that was very close to and not significantly different from what might be expected according to Boyle’s law. The TS model was estimated to be TS = 20 log L − 71.6 for the conventional relationship between TS and length, but TS = 20 log L− (20/3) log (1+z/10) − 67.6 when the depth (z, m) effect was included according to Boyle’s law. These results may have a significant influence on abundance estimates of anchovy derived from acoustic surveys, both in the Yellow Sea and in other parts of the world.

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