INVESTIGADORES
COLAUTTI Dario Cesar
artículos
Título:
ASSESSMENT OF CONDITION IN PEJERREY (Odontesthes bonariensis) POPULATIONS: WHICH INDEX WORK BEST?
Autor/es:
BAIGUN C.; COLAUTTI D. C.; GROSMAN F.
Revista:
Neotropical Ichtyology
Editorial:
Sociedade Brasileira de Ictiologia
Referencias:
Lugar: Porto Alegre; Año: 2009 vol. 7 p. 439 - 446
ISSN:
1679-6225
Resumen:
This study reviews and discusses assumptions and limitations of most common indices used for pejerrey condition assessment. The pejerrey is the most important target species in temperate freshwater fisheries of Argentina and assessment of condition has been a regular practice and common diagnostic tool. Most of fisheries studies on pejerrey applied the Fulton (K) and the cephalic index without testing whether underlying assumptions or requirements were met. Use of Relative Weight index (Wr) as a suitable alternative showed however important differences by length intervals and differed if averaged values were used instead. In the case of zooplankton abundance and pejerrey catch per unit effort for example both K and Wr indices were directly related to substock, stock and quality intervals but inversely related for preferred and memorable sizes. Condition results derived from K index application may be length biased if slope of the length-weight relationship departs from 3 (isometric) and this was the case in most of reviewed studies. We noted also that pejerrey maximum length and size structure strongly varied among populations probably due to the possibility to change its trophic niche through its adult life span under suitable ecological characteristics. Such feature not observed in other pampean species may pose limitations for comparing populations. We recommend start to using the Wr index in regular surveys to perform proper comparisons among populations and to scrutinize body condition particularly when population structure is not well known, stocking has been used for population recovery, lakes supported strongly limnological changes or metaphoetesis is observed in pejerrey populations