Calibration of fish biomass estimates from gillnets: Step towards broader application of gillnet data

Říha, Milan; Prchalová, Marie; Brabec, Marek; Draštík, Vladislav; Muška, Milan; Tušer, Michal; Bartoň, Daniel; Blabolil, Petr; Čech, Martin; Frouzová, Jaroslava; Holubová, Michaela; Jůza, Tomáš; Moraes, Karlos R.; Rabaneda‐Bueno, Rubén; Sajdlová, Zuzana; Souza, Allan T.; Šmejkal, Marek; Vašek, Mojmír; Vejřík, Lukáš; Vejříková, Ivana; Peterka, Jiří; Kubečka, Jan

doi:10.1016/j.ecolind.2023.110425

Cited by 6 publications

(1 citation statement)

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“…On the other hand, these methods provide absolute estimates of abundance and biomass per volume and area of water at a given period (as also shown in this study), which is not the case for gillnets. Although an attempt has recently been made to determine the relationship between relative gillnet catch and absolute fish catch using active sampling methods (Říha et al, 2023), estimating absolute fish abundance and biomass based on gillnet catches is difficult. Gillnets can be used to compare the species composition and relative density of fish in different water bodies, but in view of the restricted migration times of fish, which influence the probability of being caught (Prchalová et al, 2010), gillnets are not a suitable method for investigating diurnal patterns in fish distribution.…”

Section: Discussionmentioning

confidence: 99%

Spatial fish distribution in autumn in a shallow mesotrophic lake, assessed by hydroacoustic surveys, trawling, and beach seining

Jůza,

Muška,

Blabolil

et al. 2024

Journal of Fish Biology

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Day and nighttime autumn fish abundance and biomass were studied in the pelagic and littoral zones of Lake Sauka in Latvia. Both pelagic methods (hydroacoustics and trawling) revealed significantly higher fish abundance and biomass during the day than at night, especially in deeper zones (below 3 m). Roach (Rutilus rutilus) and Eurasian perch (Perca fluviatilis) dominated the trawl catches during the day, while roach and ruffe dominated at night. Fish smaller than 14 cm strongly dominated in both the trawl catches and hydroacoustic observations. Our hydroacoustic sampling found inhomogeneous pelagic distributions of fish aggregated in big shoals during the day. In the littoral zone, which was sampled by beach seining, both the abundance and biomass were significantly higher at night than during the day. Roach, bleak, and European perch usually dominated in beach seine catches during the day and at night. The daytime pelagic biomass found by hydroacoustics was 62 kg/ha and it decreased to approximately 11 kg/ha at night. The littoral biomass found by beach seining was diurnally opposite, 4 kg/ha during the day and 37 kg/ha at night. It is obvious that diurnal horizontal migrations between pelagic and littoral zones, and shoaling behavior during the daytime are common patterns in the shallow Lake Sauka during the autumn. The study of the spatial distribution of fish is extremely important for the establishment of an appropriate monitoring plan for the purposes of the Water Framework Directive with regard to the morphometry of the lake, the geographical location, and the sampling period of the year. This study also shows that the combination of completely non‐invasive hydroacoustic and other methods that are invasive (trawls, beach seines) but not as destructive as gillnets, which are normally used for scientific fish monitoring in Europe, could be a future way forward for fish monitoring.

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Section: Discussionmentioning

confidence: 99%