Evaluation of electrofishing efficiency in a stream under natural and regulated conditions

Abstract

-Sampling efficiency (p), estimated from the Zippin depletion model and the percentage of fish obtained during first runs (single-pass electrofishing), which is also named relative abundance (C 1 ), calculated as the ratio of C 1 to estimated density for a site (C e ), were analysed in five contiguous sites in a small lowland stream in Poland over 23 years. The sampled reach was unregulated during the first decade of the study period, but regulated by weirs and sluices in the latter 13 years. The sites were populated with 17 fish species during this period. Sampling efficiency p calculated for all species did not differ significantly between the five sites in any given year, between benthic and non-benthic species, or between the natural and regulated periods. Differences in p were only observed between some species. C 1 differed significantly between large and small species and, except for roach, was not dependent on the number of runs. Results indicate a high stability of both sampling indices in this small stream, despite changes in channel morphology after regulation: information which could be useful for future sampling research in streams.Key words: Lowland stream / Natural / Regulated / Electrofishing efficiency / Relative abundance Résumé -Evaluation de l'efficacité de la pêche électrique en rivière en conditions naturelles et en débit régulé. L'efficacité de l'échantillonnage (p), estimée à partir du modèle de Zippin et le pourcentage de poissons obtenu durant les premiers passages, appelé aussi abondance relative (C 1 ), calculée comme le rapport de C 1 à la densité estimée pour un site (C e ), ont été analysés en cinq sites contigus, dans une petite rivière de plaine, en Pologne, sur une période de 23 ans. Le bief échantillonné était non-régulé durant les dix premières années de l'étude, puis régulé au moyen de barrages et chenaux, les treize années suivantes. Les sites étaient peuplées de 17 espèces de poissons durant cette période. L'efficacité p calculée pour toutes les espèces ne diffère pas entre les cinq sites et quelle que soit l'année, entre espèces benthiques ou non-benthiques, ou entre les périodes de régulation ou non. Des différences de p sont seulement observées entre quelques espèces. C 1 diffère significativement entre grandes et petites espèces, à l'exception du gardon, sans être dépendant du nombre de passages. Les résultats indiquent une grande stabilité des deux indices d'échantillonnage dans cette rivière, en dépit du changement de morphologie du cours d'eau après la régulation : des informations qui peuvent être utiles pour de futurs travaux relatifs à l'échantillonnage des cours d'eau.

Assemblage level monitoring of stream fishes: The relative efficiency of single-pass vs. double-pass electrofishing

“…Therefore, multiple-pass surveys may be necessary for estimating population densities if that is the objective of the study (see e.g. Cowx, 1983;Meyer et al, 2006;Penczak and Głowacki, 2008 and references herein), but are not really practical for assemblage level regional scale monitoring purposes (Meador et al, 2003; but see Kennard et al, 2006). If the purpose is to analyse spatial and temporal patterns in assemblage level attributes double-pass electrofishing may mean a compromise, because the most important variables (i.e.…”

Despite anthropogenic disturbance and moderate climate changes fish density and biomass fluctuated non directionally in a small stream

“…Application of the Zippin model is exemplified in a paper devoted to fish catchability in the Dobrzynka Stream (Penczak and Głowacki, 2008). The density and standing crop for all populations and some selected species were recalculated per 100 m 2 using means from the four sampled sites, which were 100 m long, and the central site (C), which was 50 m long.…”

“…Besides, three-four years after the river banks were strengtho n l y sides, three-four years after the river banks were strengthened with fascine to protect them against erosion in 1989, o n l y ened with fascine to protect them against erosion in 1989, ing formed shelters for fish there (Penczak and Mann, 1993). Despite of the above data some effects of channelization conducted in the middle course of the Dobrzynka Stream were expected because several low cement weirs were constructed there, and the clearance of all submerged and emerged vegetation was performed (Penczak and Głowacki, 2008). This resistance fish populations against extinction can be continues even when rivers become regulated (Shuter and Meisner, 1992;Jackson et al, 2001;Parasiewicz, 2008), for example when naturally vegetated banks are replaced by concrete slabs (Wootton, 1990;Matthews, 1998;Jackson et al, 2001).…”

“…Caught fish from each sample, after the identification of the species were counted, weighed and released back into the river at the end of given site. Site area of sites A, B, D and E till 1988 was over 200 m 2 each, and after channelization about 170 m 2 each; that of site C was 85 m 2 (Penczak and Głowacki, 2008). For this study, fish were sampled at the first ten day period of October, each year from 1979 to 2001, because this month freshwater fish in middle Europe achieve their maximum length, body weight, body caloricity, etc.…”

Fish-Based Indices in Catalan Rivers: Intercalibration and Comparison of Approaches

“…Several studies have been conducted to balance the compromise between representativeness of fish assemblage in the sampling area and sampling cost (e.g., time, staff, and expenditure), including the comparison of single-vs. multiple-pass electrofishing over various habitats (e.g., [25][26][27][28][29][30]), and the analysis of electrofishing equipment type (e.g., [31]) and suitable sampling length [30,[32][33][34][35][36][37]. However, little attention has been paid to assess the differences of catchability among electrofishing crews and equipment and the effects of sampling frequentation in Mediterranean regions.…”