Spatial heterogeneity and species responses to anthropogenic disturbance: A test for generality.

GUTIERREZ, J.L; M.G. PALOMO; O. IRIBARNE

FISHERIES RESEARCH

Elsevier

Lugar: Amsterdam; Año: 2004 vol. 67 p. 55 - 70

0165-7836

Small-scale artisanal fisheries of the stout razor clam Tagelus plebeius are currently developing in intertidal habitats of several southwestern Atlantic estuaries (36–39◦S) in many cases conflicting with habitat conservation. We evaluated the effects of this harvesting on non-target benthic species with replicated experiments conducted simultaneously at six different locations. Given the tendency of burrowing crabs Chasmagnathus granulata to rapidly colonize disturbed plots and excavate new burrows, our a priori prediction was that local effects of clam harvesting would vary depending on the local density of burrowing crabs because it may determine contrasting levels of burrowing disturbance after clam harvesting. To test this hypothesis, experimental plots were distributed equally between habitats characterized by contrasting levels of burrowing crab density. Contrary to our expectation, burrowing crabs recolonized all the disturbed plots at similar rates. The effects of clam harvesting on burrowing crabs, however, varied temporally from positive at low-density mosaics to negative at high-density mosaics, probably due to temporal variations in crab wandering behavior. Juveniles of the crab Cyrtograpsus angulatus showed location-dependent positive responses to the clam harvesting treatment associated with increases in the amount of shell material exposed at the surface during harvesting. Harvesting significantly affects the density of the polychaeteTagelus plebeius are currently developing in intertidal habitats of several southwestern Atlantic estuaries (36–39◦S) in many cases conflicting with habitat conservation. We evaluated the effects of this harvesting on non-target benthic species with replicated experiments conducted simultaneously at six different locations. Given the tendency of burrowing crabs Chasmagnathus granulata to rapidly colonize disturbed plots and excavate new burrows, our a priori prediction was that local effects of clam harvesting would vary depending on the local density of burrowing crabs because it may determine contrasting levels of burrowing disturbance after clam harvesting. To test this hypothesis, experimental plots were distributed equally between habitats characterized by contrasting levels of burrowing crab density. Contrary to our expectation, burrowing crabs recolonized all the disturbed plots at similar rates. The effects of clam harvesting on burrowing crabs, however, varied temporally from positive at low-density mosaics to negative at high-density mosaics, probably due to temporal variations in crab wandering behavior. Juveniles of the crab Cyrtograpsus angulatus showed location-dependent positive responses to the clam harvesting treatment associated with increases in the amount of shell material exposed at the surface during harvesting. Harvesting significantly affects the density of the polychaete◦S) in many cases conflicting with habitat conservation. We evaluated the effects of this harvesting on non-target benthic species with replicated experiments conducted simultaneously at six different locations. Given the tendency of burrowing crabs Chasmagnathus granulata to rapidly colonize disturbed plots and excavate new burrows, our a priori prediction was that local effects of clam harvesting would vary depending on the local density of burrowing crabs because it may determine contrasting levels of burrowing disturbance after clam harvesting. To test this hypothesis, experimental plots were distributed equally between habitats characterized by contrasting levels of burrowing crab density. Contrary to our expectation, burrowing crabs recolonized all the disturbed plots at similar rates. The effects of clam harvesting on burrowing crabs, however, varied temporally from positive at low-density mosaics to negative at high-density mosaics, probably due to temporal variations in crab wandering behavior. Juveniles of the crab Cyrtograpsus angulatus showed location-dependent positive responses to the clam harvesting treatment associated with increases in the amount of shell material exposed at the surface during harvesting. Harvesting significantly affects the density of the polychaeteChasmagnathus granulata to rapidly colonize disturbed plots and excavate new burrows, our a priori prediction was that local effects of clam harvesting would vary depending on the local density of burrowing crabs because it may determine contrasting levels of burrowing disturbance after clam harvesting. To test this hypothesis, experimental plots were distributed equally between habitats characterized by contrasting levels of burrowing crab density. Contrary to our expectation, burrowing crabs recolonized all the disturbed plots at similar rates. The effects of clam harvesting on burrowing crabs, however, varied temporally from positive at low-density mosaics to negative at high-density mosaics, probably due to temporal variations in crab wandering behavior. Juveniles of the crab Cyrtograpsus angulatus showed location-dependent positive responses to the clam harvesting treatment associated with increases in the amount of shell material exposed at the surface during harvesting. Harvesting significantly affects the density of the polychaeteCyrtograpsus angulatus showed location-dependent positive responses to the clam harvesting treatment associated with increases in the amount of shell material exposed at the surface during harvesting. Harvesting significantly affects the density of the polychaeteshowed location-dependent positive responses to the clam harvesting treatment associated with increases in the amount of shell material exposed at the surface during harvesting. Harvesting significantly affects the density of the polychaete Laeonereis acuta in a few particular locations and sampling dates. Location-dependent increases of this species in disturbed plots were observed after recruitment events, suggesting recruitment enhancement by bottom roughness interacting with differences among locations in larval supply. These results demonstrate that extrapolation of results from a single location may be inaccurate even for nearby areas.We strongly advocate that the occurrence and nature of location-dependency should be integrated in the design of management programs. © 2003 Elsevier B.V. All rights reserved.in a few particular locations and sampling dates. Location-dependent increases of this species in disturbed plots were observed after recruitment events, suggesting recruitment enhancement by bottom roughness interacting with differences among locations in larval supply. These results demonstrate that extrapolation of results from a single location may be inaccurate even for nearby areas.We strongly advocate that the occurrence and nature of location-dependency should be integrated in the design of management programs. © 2003 Elsevier B.V. All rights reserved.