Effect of fishing pressure on the spatio-temporal variability of the parrotfish, Sparisoma cretense (Pisces: Scaridae), across the Canarian Archipelago (eastern Atlantic)

Abstract

We investigated spatio-temporal variability in the population structure of the parrotfish, Sparisoma cretense (Linnaeus, 1758), throughout the Canarian Archipelago (eastern Atlantic Ocean) with underwater visual transects. By means of a multiscaled hierarchical sampling design spanning three orders of magnitude of spatial variability (from 10 s of meters between replicated 100 m2 transects to 100 s of kilometres among islands) and four sampling times (twice a year in 2003 and 2004); we related differences between islands to differences in the degree of fishing pressure. The mean abundance of parrotfish across all counts was 6.79 ± 0.46 ind 100 m−2 (mean ± S.E., n = 768 transects), while the mean biomass was 593.81 ± 45.61 g 100 m−2 (mean ± S.E., n = 768). Abundances and biomasses of S. cretense clearly differed between islands, although they were relatively consistent between the sampling times. The different abundances and biomasses observed between islands were correlated with fishing pressure, providing evidence that fishing was responsible for the inter-island differences. Differences in the size-structure between the eastern and western islands suggest differences in the recruitment periodicity at both groups of islands, which could be related to large-scale spatial variation in the oceanographic conditions across an east–west gradient along the Canary Islands.