Coastal habitats and their significance in the early life histories of fishes in southeastern Lake Ontario

This dissertation explores the spatial dynamics of submerged aquatic vegetation with reference to the changing water clarity of nearshore and inshore habitats of Lake Ontario, and quantitatively evaluates the claims that coastal habitats are important spawning and nursery habitats for fishes in southeastern Lake Ontario.; Chapter 1 investigates the physical tolerance of submerged macrophytes and develops a generalized spatially explicit, suitability model. In large lakes, this habitat is often confined to sheltered inshore and nearshore areas, and is regarded as important spawning and nursery habitat for many Great Lakes fishes. I simulated the effects of oligotrophication on area and volume of suitable macrophyte habitat using 20 years of water clarity data. Simulated suitable area ranged from a minimum of 1.97 × 106 m 3 in 1980 to a maximum of 2.76 × 106 m 3 in 1996, and volumes ranged from 4.02 × 106 m3 in 1980 to 736.2 ha3 in 1996, representing a 33.4% and 41.2% increase, respectively.; Chapter 2 examines the distribution of larval fish biomass along a continuum of shallow water habitats from riverine marsh to shallow nearshore, at three locations along southeastern Lake Ontario. Mean dry weights of all species were significantly greater in embayments and riverine marshes than in the nearshore of the lake (P < 0.01). Mean dry weights of all species were similar among locations, pooled for all habitats (P = 0.34), however, biomass of resident marsh fishes was greatest in the location with the smallest embayment.; Chapter 3 evaluates the potential for fish larvae and eggs exported from a riverine marsh to significantly contribute to the recruitment of common carp and alewife. Mean total seasonal loads of carp larvae were 890,000 (±102,000 SD) individuals from the creek to the bay. Compared to estimates of bay-wide abundance, Irondequoit Creek contributed 1%–6.4% of the carp larvae in Irondequoit Bay. 20,200,000 (±4,600,000 SD) alewife eggs were contributed to the bay in 1998, representing 0.0001%–0.02% of the following year's yearling population. This study calls into question the frequent assessment that coastal wetlands are important sources of young fish relative to the entire basin.