Abstract

VELASCO, Andrés  and  WOLFF, Matthias. Ictiofauna juvenil de fondos blandos durante la transición de "secas" a lluvias en la costa pacífica de Colombia. Rev. biol. trop [online]. 2000, vol.48, n.1, pp.215-228. ISSN 0034-7744.

Based on ichthyoplancton research along the southern Pacific coast of Colombia, which revealed high concentrations of fish larvae in this area, a juvenil fish survey was conducted in shallow waters (<10 meter water depth) during the transition period from dry to wet season (July 21 to July 31, 1994). The twelve sampling stations, were distributed in front of the four main of this coastline, where the highest concentrations of juvenile fish were expected. At each sample station, three 15 min oblique hauls were conducted every 8 hours using a bottom trawl for juvenile fish of 4 mm mesh size; 53 species in 20 families were identified (21 not known as adults in the area). They were distributed as follows: Sciaenids (11), Ariids (7), Pristigasterids (6), Engraulids (6), Carangids (5), Clupeids (2), Soleids (2), Batrachoidids (2), Tetraodontids (2), Urolophids (1), Polynemids (1), Synodontids (1) and Taeniopedids (1). This ichthyofauna is common in open tropical estuaries. Abundances and biomass were 0.35 ind./m³ and 1.61 g/m³ respectively, higher than in other tropical shallow water systems. The niches of the 25 species whose abundance (A) and biomass (B) contributed 97.5% and 93.3% respectively to the total catches were: (1) pelagic-neritic (53% A, 34% B); (2) demersal-pelagic (18% A, 28% B); (3) demersal (22% A, 23% B) and (4) benthic (8% A, 15% B). The Shannon-Weaver diversity index in the four subareas ranged from 0.89 to 1.1, within the range reported for other tropical American estuarine systems. An ordination analysis (non-metric Multi-Dimensional Scaling, MDS) of the data revealed significant differences in the species composition between day and night and an important association among some species. Station position, tides and environmental parameters did not markedly influence species composition. It is concluded that: (1) The area surveyed represents an important nursery and growth habitat for juvenile fish of many species that are more common as adults over soft bottoms in deep waters of the continental shelf; (2) this shallow soft bottom fish community is clearly separated from those species inhabiting intertidal salt marshes, interior bays and mangrove areas; and (3) some of the fish species commonly living in rocky and reef habitats in adult stages, spend their juvenile stage over shallow water soft bottoms. These results confirm a rather strong niche separation between juvenile and adults fish species stages in tropical waters.

Keywords : Nurseries; juvenil fish assemblages; fish diversity; estuaries; multivariate analysis; Colombian Pacific Coast.