Seasonal Fish Community use of the Great Lakes Coastal Marsh Coates Paradise as reproductive habitat

Abstract

<p>Coates Paradise is a 250 ha coastal marsh, located at the western most point of Lake Ontario, adjoining Hamilton Harbour. Currently the marsh is severely degraded. Only 15% of the marsh remains vegetated, while the rest exists as an open water turbid bay. Stresses affecting the marsh include a very high carp population, excessive nutrient and sediment input, and water level regulation. Both Coates Paradise and Hamilton Harbour are the targets of an extensive remediation plan, known as the Hamilton Harbour Remedial Action Plan (HHRAP 1991 ).</p> <p>Coastal marshes are recognized for their importance as reproductive areas for the fish community. Considering the importance of marshes to fish, there is a surprising lack of information available. There have been very few comprehensive studies of whole fish communities and their use of marshes, and even fewer which address reproductive utilization. Herdendorf et. al. (1986) listed fish community structure and utilization of marshes for spawning, nursery and feeding areas as the top priorities of coastal wetland research.</p> <p>This study examines the fish community of Coates Paradise for the purpose of providing detailed information on the fish community in association with the HHRAP, as well as examining fish community use of the marsh with respect to reproductive utilization.</p> <p>The study included both temporal and spatial coverage of the marsh fish community. In an attempt to capture whole fish community data for Coates Paradise, fish community surveys were done monthly during the ice-free portion of the season. Surveys were initiated in the summer of 1994, followed by 3 full seasons between 1995 and 1997. Further to this, Coates Paradise was subdivided into 3 habitat types including off-shore, near-shore, and lower river. These habitats were further subdivided into sub-habitats, based on habitat variables that included wind fetch, nutrient enrichment, and degree of vegetation. A total of 8 sub-habitat types were included. Within each sub-habitat type four 50 m transects were located. The transects were surveyed by electrofishing.</p> <p>A total of 47,512 fish covering 47 species were captured in the study. Annual species diversity averaged 38 species, while monthly richness followed a seasonal trend with a maximum of 34 species occurring in July. Most species of fish were found to exist only in the near-shore habitat. Also the near-shore habitat had substantially more fish (Exposed sub-habitat -187 I transect) than the off-shore habitat (Bay sub-habitat -8 I transect).</p> <p>All species demonstrated migration into and out of the marsh in association with spawning periods and spawning habitat guilds. Most species of non YOY fish had highest densities at corresponding spawning times and in correlation to spawning habitat guilds. Habitat preferences of YOY species also generally reflected a species spawning habitat guild. Total non YOY populations were also generally at a peak during spawning periods. The non YOY of most species showed a distinct migration out of the marsh following spawning periods. Samples taken two months prior to a species spawning periods had almost no fish of the species occurring in the marsh, while samples taken two months following peak spawning periods resulted in almost no larger fish of a species being found in the marsh.</p> <p>The dominant fish species of the marsh was adult carp. In the electrofishing data, adult carp represented 90% of the biomass, but only 10% of the total catch. Only six other species had substantial adult population, while most other species are represent by less than 15 individuals in the data set. These six species included, brown bullhead, white sucker, gizzard shad, white perch, spottail shiner and pumpkinseed, and are reflective of the state of the harbour (the adult habitat).</p> <p>The most abundant species in the marsh include YOY of gizzard shad, white perch and spottail shiners, reflecting the marsh's role as reproductive habitat. Maximum numbers of fish occurred in late August, with as many as 800 fish being captured in a single transect. At this time the fish community consisted almost entirely of YOY fish.</p>