Search   in
between years and
A visual assessment of the inshore fishes and fishery resources off El Hierro, Canary Islands: A baseline survey
Stephen A. Bortone, James Van Tassell, Alberto Brito, Jesús M. Falcón and Charles M. Bundrick

There areindications that the recent development of the tourist industry has thepotential to cause tremendous environmental stress on the fishes and fisheryresources of the Canary Islands. More than 360 visual surveys of the total fishcommunity and 1000 visual surveys of the parrotfish (Sparisoma cretense) populationwere conducted off the most remote of the islands in the Canarian Archipelago,El Hierro, during the Summer of 1989 to determine their status and theenvironmental factors associated with their abundance. The five-minute, 100 m2, pointcount surveys were conducted to determine the number of individuals perspecies for the total community analysis and the number and size of parrotfishby sex and maturity using color type as an indicator of life stage. An ANOVAanalysis indicated that little of the variation (i.e., 34.2 %, 32.7 % and 31.1%) in the community structure (i.e., number of species, number of individualsand species diversity, respectively) could be explained by the 27 variablesrecorded during the study period. A Detrended Correspondence Analysis (DCA)indicated that species were strongly associated with substrate type as well asdistance above the substrate. Samples were grouped according to species withsimilar affinities for substrate types. A Two-way Indicator Species Analysis(TWINSPAN) showed four major groups at level 2 that also showed associationsbased on affinity for substrate type. The TWINSPAN analysis for the samplesindicated that four species (e.i., Abudefduf luridus, Thalassoma pavo,Chromis limbatus, and Sparisoma cretense were significant in therecognition of 358 of 369 samples. The ANOVA analysis of the size and abundanceof parrotfish indicated that no variable except sampling date was significantin explaining variation in size. Separate length-frequency analyses by date andcolor type indicated an increase in size for adult males and females during thesampling period. It is uncertain if our visual survey technique was reliablyable to detect growth among parrotfish during the five-week sampling period.The average standing biomass of 399 grams of parrotfish per 100 m* is considered substantial and should de carefully monitored to detect changes in thefishery resource attributable to parrotfish.

Keywords: Fisheries, Census, Parrotfish, Length-frequency, biomass, DCA,TWINSPAN, substrate.
Contents of this volume Sci. Mar. 55(3) : 529-541 Back PDF
Please, send comments to
ICM (CSIC) - Passeig Marítim de la Barceloneta, 37-49. E-08003 Barcelona (Spain)