Changes in the fish fauna associated with a sub-Antarctic Macrocystis pyrifera kelp forest in response to canopy removal

Abstract

The fish fauna associated with a Macrocystis pyrifera forest and the effects of the canopy removal on this fauna were studied in the Beagle Channel, Tierra del Fuego. Seasonal changes and differences in the fish communities that inhabit the canopy and the holdfast were also studied. Two patches of kelp forest separated by 200 m were selected. In one, the canopy was removed periodically while the other was used as a control. Samples were collected seasonally, from autumn 1999 to 2001. Fish fauna in the water column was sampled using trammel nets and holdfast fish fauna was sampled by removing the complete holdfast. Different assemblages of fish species were captured in the water column (surface and bottom) and in the holdfast. In the former there were mainly pelagic and benthopelagic species and the latter predominantly demersal species. The principal effect of the Canopy removal was a drop in the abundance (and total weight) of Paranotothenia magellanica (doradito), the species with the strongest relationship with the canopy, principally at the surface of the treated patch probable due to a reduction in the availability of refuges. A high degree of seasonality was observed for fish species’ total weight, abundance and diversity, with higher values in summer and autumn. Taking into account our data and available data on kelp growth in the same locality, we suggest of cutting the kelp forest (preferably those farther away from the coast) once a year in winter or early spring, in order to minimize impact on the fish community.