FLUME WEIR FOR QUANTITATIVE COLLECTION OF NEKTON FROM VEGETATED INTERTIDAL HABITATS

I describe a flume weir for long-term quantitative sampling of nekton from vegetated intertidal marshes at high tide. The flume weir design is a significant advance over previous methods because it samples a relatively large and precisely defined area (100 m2) without affecting the normal movement patterns of nekton into or out of the sampling area until the moment a sample is required. Sampling by flume weir is neither destructive of the vegetated habitat nor restricted to the marsh edge as are many other methods recently used to sample nekton in intertidal marshes. The mean efficiency with which fish and crustaceans greater-than-or-equal-to 30 mm in length were recovered from flume weirs was in the range 86 to 99 %. From July 1988 to June 1990, 20 species of fish and 4 species of crustaceans comprising a total of 47 353 individuals (15 to 540 mm in length) were collected in 271 flume weir samples taken from intertidal marsh sites adjacent to Sapelo Island, Georgia, USA. Adults and juveniles of small resident marsh species composed 82.3 % of the total individuals collected. Juveniles of seasonal migrant species, which use marshes as nurseries were also common. The most abundant of these was the white shrimp Penaeus setiferus, which was present only from June to November, but composed 12.9 % of the total nekton collected. Other common seasonal species were mullet Mugil spp. and spot Leiostomus xanthurus, which represented 1.7 and 1.6 % of the total catch, respectively. By providing a means of monitoring nekton densities at sites where conventional gears are clearly inappropriate, the flume weir may allow researchers to address long-standing questions linking marsh production with coastal fisheries. As a management tool, the flume weir may be used by coastal land managers to assign a fisheries value to specific intertidal habitats as part of a process to evaluate marsh mitigation and restoration efforts.