%0 Journal Article
%T Relationship between horizontal hydroacoustic stock estimates and gillnet catches of surface-oriented fish in shallow Lake Balaton (Hungary) Relation entre les estimations horizontales hydroacoustiques du stock et les captures au filet maillant de poissons de surface en eaux peu profondes du lac Balaton (Hongrie)
%A Gy£¿rgy ¨¢.I.
%A T¨¢trai I.
%A Speczi¨¢r A.
%J Knowledge and Management of Aquatic Ecosystems
%D 2012
%I EDP Sciences
%R 10.1051/kmae/2012012
%X 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. Nous avons examin¨¦ si les filets maillants et l¡¯hydroacoustique fournissent des donn¨¦es comparables de la densit¨¦ des poissons et des estimations de distribution en taille des poissons dans la couche d¡¯eau sup¨¦rieure d¡¯un lac peu profond trouble et si l¡¯inclusion de param¨¨tres environnementaux et du stock de poissons pourrait am¨¦liorer la comparabilit¨¦ des donn¨¦es entre les diff¨¦rents engins. Selon la p¨ºche au filet maillant, la plupart des poissons de longueur totale inf¨¦rieure ¨¤ 14 cm ¨¦taient Alburnus alburnus, et la plupart des poissons de plus de 14 cm ¨¦taient Pelecus cultratus. Les distributions de taille et les tailles m¨¦dianes obtenues ¨¤ partir des filets maillants et de l¡¯acoustique sont diff¨¦rentes. Les estimations d¨¦riv¨¦es de la seule densit¨¦ acoustique ne repr¨¦sentaient que moins de 8,8 % de la variation des captures au filet maillant en nombre et aucune corr¨¦lation n¡¯a ¨¦t¨¦ trouv¨¦e dans les indices de biomasse. La plupart des variations observ¨¦es dans les captures par unit¨¦ d¡¯effort des filets maillants ont ¨¦t¨¦ associ¨¦es ¨¤ la transparence de l¡¯eau, aucune des autres variables ¨¦tudi¨¦es n¡¯ont un important pouvoir explicatif. Nous concluons que la possibilit¨¦ d¡¯¨¦tablir un mod¨¨le puissant d¨¦crivant la relat
%K gillnet
%K side-looking hydroacoustics
%K comparability of data
%K Alburnus alburnus
%K shallow lake
%K filet maillant
%K hydroacoustique lat¨¦rale
%K comparabilit¨¦ des donn¨¦es
%K Alburnus alburnus
%K lac peu profond
%U dx.doi.org/10.1051/kmae/2012012