Nonintrusive methods for biomass estimation in aquaculture with emphasis on fish: a review

Fish biomass estimation is one of the most common and important practices in aquaculture. The regular acquisition of fish biomass information has been identified as an urgent need for managers to optimize daily feeding, control stocking densities and ultimately determine the optimal time for harvesting. However, it is difficult to estimate fish biomass without human intervention because fishes are sensitive and move freely in an environment where visibility, lighting and stability are uncontrollable. Until now, fish biomass estimation has been mostly based on manual sampling, which is usually invasive, time‐consuming and laborious. Therefore, it is imperative and highly desirable to develop a noninvasive, rapid and cost‐effective means. Machine vision, acoustics, environmental DNA and resistivity counter provide the possibility of developing nonintrusive, faster and cheaper methods for in situ estimation of fish biomass. This article summarizes the development of these nonintrusive methods for fish biomass estimation over the past three decades and presents their basic concepts and principles. The strengths and weaknesses of each method are analysed and future research directions are also presented. Studies show that the applications of information technology such as advanced sensors and communication technologies have great significance to accelerate the development of new means and techniques for more effective biomass estimation. However, the accuracy and intelligence still need to be improved to meet intensive aquaculture requirements. Through close cooperation between fisheries experts and engineers, the precision and the level of intelligence for fish biomass estimation will be further improved based on the above methods

Report of the Working Group on Fisheries Acoustic Science & Technology (WGFAST) [18–22 May 2009 Ancona, Italy]

Contributors: Lucio Calise, Nils Håkansson, Rolf Korneliussen, Hector Peña and Eirik Tenninge

Community Structure and Feeding Ecology of Fishes on Artificial Reefs in the Northwest Gulf of Mexico

Artificial reefs serve as important habitat for several marine fish species in the northwest Gulf of Mexico (NW GoM). Structure type, relief, and depth of artificial reefs have been shown to affect the community composition and trophic relationships of reef associated fishes. The purpose of this study is to investigate these relationships using a variety of metrics examining both fish assemblage and trophic ecology on several nearshore artificial reefs in the northwest Gulf of Mexico. Chapter I uses a suite of traditional fisheries methods to observe the effects of individual structure on the assemblage of marine fish. We investigated three individual reef types (concrete, rig, and ship) using three survey methods (fish trap, vertical longline, and active acoustics) over four years of sampling (2014 -2017). Two reef types, rig and ship, were found to have a more diverse assemblage of fish than concrete reefs using traditional fishing methods (vertical longline and fish trap); however, concrete reefs were found to have higher concentrations of fish using active acoustics. These results indicate that increased reef relief and complexity offer habitat for a wider range of species, while low relief habitats attract less diverse assemblages of fish in higher concentrations. The differences in trophic structure were also investigated on high and low relief structure types in Chapter II. Using both stable isotope and fatty acid analyses we examined the feeding ecology of three reef associated fishes, tomtate (Haemulon aurolineatum), pigfish (Orthopristis chrysoptera), and red snapper (Lutjanus campechanus). The three species were compared on high relief habitats, while one species, red snapper, was also investigated on low relief habitats. The three species exhibited different feeding strategies using stable isotope values and fatty acid ratios that reflected known diets from other regions. Red snapper feeding ecology was different between the two structure types. Red snapper that were collected on low relief habitats fed on a higher trophic level than those collected on high relief habitat types. This difference among the structure types may be due to the lack of intraguild competition that may occur on more diverse high relief reefs relative to less diverse low relief reefs. Overall results suggest that artificial reef structure type and design may support unique assemblages and provide different functions to reef associated species

Assessing Horizontally-oriented Acoustic Methods for Gizzard Shad Abundance Assessments: Accuracy, Precision and Target Orientation

Gizzard Shad (Dorosoma cepedianum) are an important prey species that are commonly sampled with gill nets. However, horizontally-oriented methodologies have the potential to produce better Gizzard Shad data with less effort. Before horizontal beaming can be used as a sampling gear for Gizzard Shad, accuracy and precision need to be examined to determine if this approach provides reliable and consistent data. Further, Gizzard Shad-specific relationships between acoustic target strength (TS) and total length (TL) should be derived to ensure density estimates are accurate. I tested the accuracy and precision of horizontal beaming by sampling known populations of Gizzard Shad in a net pen (15-m long x 15-m wide x 4.5-m deep with 6.35-mm square mesh). I found horizontal beaming accurately detected changes in density (R2=0.63) with increased precision (mean CV of 6% among all trials) than other gears used to sample Gizzard Shad. Given that TS changes with fish orientation, I developed an orientation-based TS-TL equation to increase accuracy of hydroacoustic estimates. A catenary (U-Shape) function was best at representing the change in TS at different fish orientations (conditional R2 = 0.71 and marginal R2 = 0.67). I also compared echo integration results using six different TS-TL equations (2 from this paper and 4 from previous literature) using 23 fish aggregations imaged in the field. Equation choice had a significant effect on density estimates (P<0.01) indicating care should be taken when selecting TS-TL equations for use in hydroacoustic surveys.Natural Resources and Ecology Managemen

Towards an optimal design for ecosystem-level ocean observatories

Four operational factors, together with high development cost, currently limit the use of ocean observatories in ecological and fisheries applications: 1) limited spatial coverage; 2) limited integration of multiple types of technologies; 3) limitations in the experimental design for in situ studies; and 4) potential unpredicted bias in monitoring outcomes due to the infrastructure’s presence and functioning footprint. To address these limitations, we propose a novel concept of a standardized “ecosystem observatory module” structure composed of a central node and three tethered satellite pods together with permanent mobile platforms. The module would be designed with a rigid spatial configuration to optimize overlap among multiple observation technologies each providing 360° coverage around the module, including permanent stereo-video cameras, acoustic imaging sonar cameras, horizontal multi-beam echosounders and a passive acoustic array. The incorporation of multiple integrated observation technologies would enable unprecedented quantification of macrofaunal composition, abundance and density surrounding the module, as well as the ability to track the movements of individual fishes and macroinvertebrates. Such a standardized modular design would allow for the hierarchical spatial connection of observatory modules into local module clusters and larger geographic module networks, providing synoptic data within and across linked ecosystems suitable for fisheries and ecosystem level monitoring on multiple scales.Peer ReviewedPostprint (author's final draft