Fish Size Distribution Research Articles

Habitat-specific effects of particle size, current velocity, water depth, and predation risk on size-dependent crayfish distribution

This study assessed effects of abiotic (current velocity, water depth, particle size) and biotic (predation risk for crayfish, size distribution and densities of predatory fish) variables on habitat- and size-specific distribution patterns of lotic crayfish (Orconectes obscurus) using field surveys and tethering experiments. Additionally, particle size manipulations were used with predation assays to assess habitat-specific interactions since the average particle size increased from deep pools to shallow pools to riffles. Large crayfish had the highest densities in deep pools and were associated with increased water depth, whereas small and medium crayfish had the highest densities in shallow pools and were strongly associated with increased particle size and decreased water depth. Regardless of size, crayfish in deep pools had significantly lower survival than in shallow pools and riffles. However, only small crayfish showed consistent differences in predation risk by habitat type and were significantly more vulnerable to predation than larger crayfish. Additionally, large rocky refugia resulted in significantly higher survival of small crayfish in the combined particle manipulation/tethering experiment. Overall, predation appears to be a key mechanism structuring habitat-specific distribution patterns for only small O. obscurus. Large substrates may be particularly important in habitats where both small crayfish density and predation risk are high.

SIZE AND FISHING GROUND OFWAHOO (Acanthocybium solandri Cuvier, 1832) FROM CATCH DATA OF TUNA LONGLINE OPERATED IN INDIAN OCEAN

Wahoo (<em>Acanthocybium solandri</em> Cuvier, 1832) is a member of the Scombrid family, is a pelagic (open ocean) species found worldwide in tropical and warm-temperate seas. It is fished throughout its range by artisanal, recreational, and commercial. Wahoo is one of the by-product species of the tuna long line fleets operate in Indian Ocean. This paper describes status of wahoo resource caught by tuna long line in Indian Ocean based at Benoa-Bali. Data obtained from onboard observer program on the tuna long liner based at Benoa-Bali during 2005-2010. Total of 85 trips of onboard observation were carried out with the total long line sets (one set per day) were 2873 times. The data covered the horizontal and vertical position of tuna long line hooks caught the wahoo, hook rate and fish size distribution. Data of horizontal fishing positions (coordinates) gained from the global positioning system availabled in the tuna long liners. The depth of the long line gear in the waters and teperature of waters were measured by mini-loggers TDR type SP2T-1200, brand: NKE Micrel. Hook rate of wahoo is calculated using the Klawe (1986) method. Result of research showed that the wahoos caught by tuna long lines based at Benoa spread horizontally between 1o31’-33o 40’S and 77o18’-117o53’E and spread vertically between the depth of 75.2- 285.7 m. From 85 tuna long line fishing trips, only about 50% of 85 tuna long line fishing trips caught wahoo with hook rate ranged 0.947-1.399 per 1000 hooks/setting. Size distribution of wahoo ranged 70-180cm with modus ranged 101-110cm.

Non-indigenous amphidromous sculpin Cottus pollux small-egg type (Teleostei: Cottidae) detected in rivers entering the Sea of Japan off Honshu Island, Japan

The amphidromous sculpin Cottus pollux small-egg type (SE) is an endemic species in rivers that flow into the Pacific Ocean on the east side of Honshu Island, Japan. However, our molecular genetic and morphological analyses using recently collected specimens showed that C. pollux SE inhabits some rivers flowing into the Sea of Japan, where this species is originally non-indigenous. Thus, these results suggest that C. pollux SE was anthropogenically introduced into these rivers. In addition, our data on the size distribution of juvenile fishes suggest that non-indigenous C. pollux SE reproduce at least in rivers of Ishikawa Prefecture.

Relationship between horizontal hydroacoustic stock estimates and gillnet catches of surface-oriented fish in shallow Lake Balaton (Hungary)

We examined whether gillnetting and hydroacoustics provide comparable relative fish density and fish size distribution estimates in the uppermost water layer of a shallow turbid lake and whether the inclusion of environmental and stock parameters could improve comparability of data between different gears. According to gillnetting, most fish shorter than 14 cm in total length were Alburnus alburnus, and most fish longer than 14 cm were Pelecus cultratus. Size distributions and median sizes obtained from gillnetting and acoustics differed. Pure acoustics-derived density estimates accounted for only <8.8% of the variation in the gillnet catch by number and no correlation was found in biomass indices. Most variances observed in the gillnet catch-per-unit-effort data were associated with water transparency, none of the other investigated variables had significant explanatory power. We conclude that the feasibility of establishing a powerful model describing the relationship between fish density estimates of gillnetting and acoustics is low in shallow and turbid habitats, and it might be successful only if the crucial sampling and environmental parameters affecting catch efficiency of gillnets and post-processing of acoustic data are considered. This study cautions again that gillnetting should be used carefully to analyse trends of fish abundance.

Assessment of fish assemblages in coastal lagoon habitats: Effect of sampling method

The structure of fish assemblages accounted for by different sampling methods (namely fyke net, seine nets, visual census) applied to vegetated and unvegetated lagoon habitats was investigated in terms of species composition, functional groups (ecological and trophic guilds), and fish size distribution. Significant differences were detected among methods, even among similar ones (seine nets). Visual census and fyke net detected more easily pelagic species, allowing the sampling of larger fish, whereas seine nets targeted more efficiently benthic-demersal species, with a dominance of 2–10 cm size classes in the fish catches. Differences were detected also among habitats, reflecting the different fish assemblages associated to vegetated and unvegetated habitats in coastal lagoons and transitional waters. However a different ability of discriminating between habitat-associated fish assemblages was recorded for the sampling methods. The different selectivity and functioning of the tested sampling methods confirm the importance of considering the targeted scale at which the research is being carried out, as well as the method that will be used to assess the ecological status of lagoon fish assemblages when choosing the most appropriate sampling method. A cross-validation of fish sampling methodologies in transitional waters is necessary to cope with the mandatory of the Water Framework Directive of standardization and comparability of monitoring methods.

Interpreting the large fish indicator for the Celtic Sea

AbstractShephard, S., Reid, D. G., and Greenstreet, S. P. R. 2011. Interpreting the large fish indicator for the Celtic Sea. – ICES Journal of Marine Science, 68: 1963–1972. The large fish indicator (LFI) was developed in the North Sea as a size-based indicator of fish community state. It is now established as OSPAR's fish community Ecological Quality Objective (EcoQO) metric and will be applied across all OSPAR regions. To produce a protocol for use when developing regional LFIs, the North Sea experience is interpreted using data from the Celtic Sea. Differences in fish community species composition and size distribution were reflected in a different species complex and large fish threshold (50 cm) for the Celtic Sea LFI. However, a lag of 12–14 years in the relationship between assemblage-averaged fishing mortality Fcom,y and the LFI suggested similar underlying ecological mechanisms to the North Sea. The indicator responded to changes in small fish biomass that follow fishing-induced changes in the level of predation by large demersal piscivores. The Celtic Sea LFI showed maximum observed values &gt;0.40 before 1990, and 0.40 is here proposed as an EcoQO. Development of regional LFIs demands a flexible process rather than a strictly prescriptive protocol.

A method of detecting patterns in mean lengths of samples of discarded fish, applied to the self-sampling programme of the Dutch bottom-trawl fishery

Abstract Uhlmann, S. S., Bierman, S. M., and van Helmond, A. T. M. 2011. A method of detecting patterns in mean lengths of samples of discarded fish, applied to the self-sampling programme of the Dutch bottom-trawl fishery. – ICES Journal of Marine Science, 68: 1712–1718. In 2009, a self-sampling programme was organized in the Netherlands, fishers sampling ca. 80 kg of discards from randomly selected bottom trawls in the North Sea. A statistical procedure is proposed to highlight samples, trips (with multiple samples), or vessels (which may have multiple trips within a year) where extreme mean lengths of discarded fish were observed. Randomization methods were used to test for evidence of non-randomness in patterns of highlighted discard samples, e.g. repeated observations of extreme mean lengths for consecutive discard samples across trips from the same vessel. European plaice (Pleuronectes platessa), common dab (Limanda limanda), grey gurnard (Eutrigla gurnardus), and whiting (Merlangius merlangus) were considered because these were the most abundant species in most of the discard samples. A linear mixed model was used to estimate random-sample effects on the estimated mean lengths by species. These random effects were incorporated into uni- and bivariate procedures to identify extreme samples that were summed for each vessel, and the probability of observing such numbers was estimated. Excluding these samples from the dataset had marginal effects on estimated size distributions of fish.

Body size distributions in North American freshwater fish: large‐scale factors

ABSTRACTAim To document continental‐ and regional‐scale variation in the size distributions of freshwater fish and examine some energetic, evolutionary and biogeographic explanations for these patterns.Location North America.Methods Regional species lists, coupled with habitat and body size information, were used to document the spatial patterns.Results At the continental scale, riverine specialist fishes show a unimodal, right‐skewed, body size distribution whereas habitat generalist and lacustrine specialist species exhibit bimodal size distributions, with only a slight preponderance of small‐mode species. Most large‐mode species are migratory. Resident species, unlike migratory ones, show a latitudinal increase in mean size, but the size increase across all species is steeper because the importance of large migratory species increases with latitude. Size distributions change from right‐ to left‐skewed with increasing latitude. Maximum body size does not change with increasing family richness but minimum size declines and skewness increases, consistent with diversification of small species. Skewness does not vary with mean family body size.Main conclusions Post‐glacial recolonization by large, habitat generalist, migratory species is the main determinant of latitudinal size distribution trends. There is little support for the energetic hypothesis, but the data are consistent with a negative Cope's rule.

Stocking homogeneous size groups does not improve growth performance of Senegalese sole ( Solea senegalensis, Kaup 1858) juveniles: Individual growth related to fish size

Growth of homogenous sized groups was studied in captive populations of Senegalese sole ( Solea senegalensis, Kaup) juveniles. An initial sole population was graded and three different sole stocks were obtained according to their respective size to form the homogenous sized experimental groups: small, medium and large, with mean weights (±SD) of 125.5 ± 22.3, 187.8 ± 34.0 and 285.9 ± 39.3 g, respectively. A fourth sole population was established from randomly selected juveniles from every stock to constitute the ungraded control subpopulation (mean weight of 155.1 ± 57.8 g). Fish were individually tagged and their specific growth rates (SGR) registered throughout two months. Growth of the three subpopulations originally graded in small, medium and large sized soles, was always similar ( P > 0.05) at any time (approximately 0.50% day −1). After 60 days of culture, the SGR of the ungraded group was higher ( P > 0.05) than that for the sole groups with more uniform size. Grading soles also affected to SGR distributions, revealing significantly narrower profiles ( P < 0.05) from day 20 in graded groups with respect to the one that remained ungraded. A correlation between individual SGR and sole weight revealed the independency ( P > 0.05) between fish size and respective growth. This lack of correlation between individual growth and fish size is in accordance with the observed tendency of every subpopulations to achieve similar size dispersal (evaluated in terms of delta coefficient of variation, ΔCV) after 60 days of culture, regardless whether or not a previous grading was performed. Results from this work support that group heterogeneity improves the overall growth, probably associated to an efficient social arrangement. Furthermore, a hierarchy establishment independent of fish size is indicated. It is suggested that fish size distribution is the consequence of the hierarchical structure, instead of the cause of it. Results obtained in present work might be valuable in the design of improved growing strategies for S. senegalensis.

Size and Age at Maturity of Bluegill (Lepomis macrochirus) in Southeastern South Dakota Impoundments

ABSTRACT Both social and demographic factors can affect size structure of bluegill (Lepomis macrochirus) populations, but these two factors have not been assessed in South Dakota impoundments. We compared length and age at maturity of bluegill in four southeastern South Dakota impoundments (two with historically low size structure and two with historically high size structure and related bluegill growth patterns to size structure and relative abundance. Despite large differences in size structure and maximum observed total lengths among lakes, all males from three of four populations were mature by age 3, with the only exception being Lake Mitchell (high size structure population; 89% mature). Mean total length at 100% maturity was lower in the two low size structure populations, and bluegill in the two low size structure populations matured at a smaller length than in the two high size structure populations; however, at least 50% of males in all four systems reached sexual maturity by 140mm in all years. Negative relationships between mean catch-per-unit-effort and both proportional size distribution (r2 =0.47) and proportional size distribution of preferred length fish (r2 =0.86) values for all populations indicated that density-dependence was likely in these systems. Indications of social influence on bluegili behavior were observed; however, density-dependence was likely more influential on size structure.

Sewage pollution impact on Mediterranean rocky-reef fish assemblages

The effects of sewage outfalls on subtidal fish assemblages were studied along the NW coasts of Malta (Sicily channel, Mediterranean Sea) by means of underwater visual census. The presence of two spatially distinct outfalls discharging untreated wastewaters allowed to use a balanced symmetrical after control/impact (ACI) design that consisted of two putatively impacted locations and two controls, with four sites nested in each location. Surveys were performed in 2006 at two random dates. The study highlighted significant changes at both assemblage and individual species levels. Fish assemblages structures were different between controls and sewages, where total abundance of fish were higher. The responses of individual species to sewage pollution were mostly related to an anomalous increase of two small opportunistic species i.e. Gobius bucchichii and Parablennius rouxi and to a decrease of species of the genus Symphodus, particularly S. roissali and S. ocellatus. Moreover in correspondence of the outfalls, significant changes of the fish size distribution were detected for several species. These results support the use of fish assemblages as biological indicators for marine coastal waters and demonstrated the possibility to obtain sharp signals of environmental impact from some individual fish species.

Effects of grading on heritability estimates under commercial conditions: A case study with common sole, Solea solea

Breeding programs in aquaculture typically use family rearing of fry until tagging size is reached. After tagging, fish are preferably reared communally. However, communal rearing promotes social interactions such as competition for access to food. In commercial conditions, negative social effects are reduced through grading of similar sized fish into one tank. In breeding programs with selection on size related traits, grading of communally reared untagged fish potentially introduces bias in estimates of genetic parameters as tank effects might be confounded with genetic potential. We evaluated effects of grading on estimated heritability of the graded trait body length using data from simulated populations with different heritabilities and a “real” dataset of common sole, Solea solea. Datasets were sorted into eight “classes” of equal “size range”. Six size ranges were chosen to represent different time points after grading. Here it was assumed that after grading, size range of classes increases with time. Consequently, overlap of classes increases, diluting confounding tank effects and genetic effects. Ranges of classes varied from 100% total size range (full overlap of classes) to 12.5% total size range (no overlap of classes). In addition, the real dataset was analyzed with the observed size distribution of animals over tanks. In the simulated datasets heritability of body length was underestimated in similar patterns when the size range of classes comprised less than 65% of the total size range. In the real dataset, estimated heritability for body length was 0.28 (± 0.11). However, extrapolation with results from simulation showed that a heritability of 0.40 (± 0.13) can be expected. Grading had a minor effect on estimated heritability of the correlated trait body weight ( h 2 = 0.21 ± 0.09). This study demonstrates that upper estimates of heritabilities can be obtained in conditions with grading when size distributions of fish over tanks are known.

Effects of deep-water coral banks on the abundance and size structure of the megafauna in the Mediterranean Sea

Abstract The Santa Maria di Leuca (SML) coral banks represent a rare example of living Lophelia-Madrepora -bearing coral mounds in the Mediterranean Sea. They are located between 350 and 1100 m in depth, in the northern Ionian Sea (eastern-central Mediterranean). Using a multi-beam echo sounder, side-scan sonar, high-resolution seismics and underwater video, the zones were identified for the sampling demersal fauna without damaging the coral colonies. During September–October 2005 experimental samplings were carried out with longlines and trawl nets inside the coral habitat and outside, where fishery exploitation occurs. No significant differences were shown between the abundance of fish recorded using longlines in the coral and non-coral habitat even though some selachians and teleosts were more abundant in the former than in the latter. Large specimens of rockfish ( Helicolenus dactylopterus ) and blackspot seabream ( Pagellus bogaraveo ) were commonly caught using longlines in the coral habitat. Data from trawling revealed refuge effects in the coral habitat and fishing effects outside. Significant differences were detected between the recorded abundances in the two study areas. Greater densities and biomasses were obtained inside the coral area, and fish size spectra and size distributions indicate a greater abundance of large fish inside the coral habitat. The SML coral habitat is a spawning area for H. dactylopterus . The remarkable density of the young-of-the-year of the deep-water shark Etmopterus spinax as well as of Merluccius merluccius , Micromesistius poutassou , Phycis blennoides and H. dactylopterus , indicates that the coral habitat also acts as nursery area for these demersal species, which are exploited outside. Considering the evidence of the negative impact of bottom trawling and, to a lesser extent, of longlining, the coral banks can provide a refuge for the conservation of unique species and habitats as well as in providing benefit to adjacent fisheries through the spill-over effect both of eggs, larvae, juveniles and adults.

The Frequency and Length Dependence of the Target Strength of the Largehead Hairtail (Trichiurus lepturus) in Korean Waters

The largehead hairtail (Trichiurus lepturus) is one of the most common fisheries stocks in the East China Sea and the Yellow Sea. The species is caught using a variety of fishing tools, such as a stow net or a long line, as well as jigging and trawling. Scientific investigations have been conducted throughout the world to enable evidence-based estimations for the management and protection of the main fisheries biomass. For example, inshore and offshore hydro acoustic surveys are performed annually using bottom- and mid-water trawls around the Korean Peninsula. However, to date, no acoustic survey has been conducted to estimate fish size distribution, which is necessary to construct a data bank of target strength (TS) relative to fish species, length (L), and frequency. This study describes the frequency and length dependence of TS among fishes in Korean waters for the purpose of constructing such a TS data bank. TS measurements of the largehead hairtail were carried out in a water tank (L 5 m<TEX>$\times$</TEX>width 6 m<TEX>$\times$</TEX> height 5 m) at frequencies of 50, 75, 120, and 200 kHz, using a tethering method. The average TS patterns were measured as a function of tilt angle, ranging from <TEX>$-45^{\circ}$</TEX> (head down) to <TEX>$+45^{\circ}$</TEX> (head up) every <TEX>$0.2^{\circ}$</TEX>. The length conversion constant (<TEX>$b_{20}$</TEX>) was estimated under the assumption that TS is proportional to the square of the length. In addition, in situ TS measurements on live largehead hairtails were performed using a split beam echo sounder.

Fish species and size distribution and abundance in different areas in Lake Victoria, Tanzania

The study was carried out to investigate fish species distribution and abundance in different areas and size structure variations according to depth in Lake Victoria, Tanzania. Data were collected using a bottom trawl net during rainy and dry seasons in 2002. The results show that there were significant differences in catch rates between rainy and dry seasons (F (12, 12) = 2.69; p < 0.05). The rainy season recorded higher catch rates (36.25 - 106.61 kg/hr) than during the dry season (14.30 - 67.90 kg/hr). The haplochromines catch rates were higher during the dry season (11.08 kg/hr) than during the rainy season (7.72 kg/hr), however, the differences were not significant (&#61539;2 = 0.60, df = 1, p > 0.05). The distribution of the fish species in different areas recorded a significant difference during the dry season (Q = 18.254, df = 8, P < 0.001), while during the rainy season the difference was not significant (Q = 10.667, df = 8, P > 0.001). Moreover, the results show that small individuals dominated in shallow waters at a mode ranging between 15 cm and 25 cm TL. Larger individuals dominated in deep waters recording a mode at 45.5 cm TL. The study therefore, suggests that in order to have a sustainable fishery, L. niloticus should actively be exploited at depths greater than 20 m where there are larger and mature individuals. Tanzania Journal of Science Vol. 31 (1) 2005: pp. 73-82

Differences in reproductive seasonality of the Central American cichlidCichlasoma urophthalmusfrom three ‘cenotes’ (sinkholes)

Summary A total of 966 cichlids, Cichlasoma urophthalmus, was sampled from three karstic water bodies (cenotes) in the Yucatan Peninsula. Sex ratio was not different from 1. Specimens with ripe eggs were found during the dry and rainy seasons in the inland cenote and during the dry, rainy, and north winds seasons in the two wetland cenotes. With respect to relative fecundity, data show the C. urophthalmus inland population as two- to three-fold greater (53.1 ± 27.7) than the wetland populations (15.7 ± 5.1 and 18.2 ± 3.1). This is attributable to the different breeding strategies of C. urophthalmus populations inhabiting these two types of cenotes. In particular, the ichthyofauna from the two wetlands showed not only higher species richness (17 and 16 species) but also a higher number of potential predators (nine and eight species) as compared to the inland cenote (six species; two potential predators). It is hypothesized that C. urophthalmus adjusts its clutch size and extends its breeding periods as a response to riskier sites as compared to more secure ones; a higher competition for breeding sites and to increased fishing mortality.

Comparison of fish size distribution and fish abundance estimates obtained with hydroacoustics and gill netting in the open water of a large shallow lake

The distribution and overall fish abundance, and biomass of fish populations in the open water of meso-eutrophic Lake Balaton were studied in 2003-2007 using hydroacoustics and gill nets. Gillnet catches revealed that bleak (53-76 %) common bream (8-42 %), white bream and razor fish (2-18 %) dominated in the open water of the lake. Comparisons of target strength distribution from hydroacoustics and length distribution from the gillnets showed that the fishing gear did not quantitatively catch the smallest and largest size groups of fish. Mean acoustic fish abundance and biomass fluctuated significantly between both basins and years. The biomass of fish populations reflects the trophic gradient along the longitudinal axis of the lake (min-max.: 89-181 kg ha-1) showing a decreasing trend with years. The mean acoustic fish biomass was significantly higher in the eutrophic western basin, compared with mesotrophic eastern and middle ones.

The Repeatability of Fish Biomass and Size Distribution Estimates Obtained by Hydroacoustic Surveys Using Various Sampling Strategies and Statistical Analyses

AbstractSuccessive hydroacoustic surveys were conducted on a small lake in the Jura Mountains (eastern France) to test several sampling strategies and methods of calculation. The results show that night samples give a better picture of the fish populations than daytime ones; that parallel transect surveys are the ones easiest to conduct, and that, all the survey designs tested, gave statistically equivalent biomass estimations and size distributions. The results obtained are also similar for all the statistical calculation methods used. Repeated samplings on several successive days gave similar results for the estimated biomass and fish size structure in the hypolimnion, but gave different results for the fish populations in the epilimnion. As part of the Water Framework Directive monitoring of fish populations, these hydroacoustic methods can be used to estimate fish stocks, and to track their change over time and spatial differences, but they need to be combined with complementary sampling methods. (© 2008 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Length-weight relations and growth rates of dominant fishes of the Salton Sea: implications for predation by fish-eating birds

The Salton Sea is the largest lake in California. Inflows are primarily from agricultural runoff, which render it eutrophic and able to support extensive fisheries. The lake and its surrounding wetlands are critical links for the Pacific Flyway, providing refuge and food for an extensive and diverse avifauna. We document fish size distributions, body shapes and growth rates and consider how they determine availability of fish to birds. Tilapia (Oreochromis mossambicus x O. urolepis hornorum) is the most important resource for fish-eating birds. Tilapia grow fast to a size that is readily handled by large birds and are the most abundant fish in the lake. Bairdiella (Bairdiella icistia) grow to a smaller size over a longer period. Corvina (Cynoscion xanthulus), sargo (Anisotremus davidsoni), and shad (Dorosoma cepedianum) are less important for fish-eating birds because they quickly grow to sizes outside bird handling capabilities (corvina) or are not readily catchable and currently of low abundance (shad and sargo). Shape, in particular girth, determines the weight of the largest individual fish that a bird can handle; a slender 1,000 g corvina, for example, being more easily ingested than a deeper-bodied 1,000 g tilapia. Shape, however, is of secondary importance to growth rate in determining importance of a fish species in a bird's diet. Predation by corvina on tilapia and other smaller species may have historically played a large role in determining availability of fish to fish-eating birds.

Hydroacoustics as a tool for assessing fish biomass and size distribution associated with discrete shallow water estuarine habitats in Louisiana

We developed a relative index of fish biomass and size distribution in ultra-shallow waters (< 2 m) of Barataria Bay, Louisiana, based on the comparison of horizontal hydroacoustic data with gill net and push trawl catches in an effort to understand the role that habitat plays in both fish biomass and distribution. Exclosure net experiments indicated that the contribution of acoustic backscattering from sources other than fishes were negligible. Split-beam transducer, gill net, and push trawl sampling were conducted concurrently in Barataria Bay to provide information on fish composition and length distributions and for comparisons among gear types. Results suggest that acoustic fish biomass was generally higher in the low salinity stations and lower at the high salinity stations, at least in March 2004. We observed a greater mean length of fishes associated with oyster shell habitats when compared to adjacent sand-mud habitats. This paper demonstrates the utility of hydroacoustics as a tool to quantify relative acoustic fish biomass and size distribution associated with common estuarine habitats in ultra-shallow waters. This study also illustrates the potential of using acoustics for augmenting traditional sampling procedures.