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General conclusions

Larval and post-larval stages

Three habitats of permanent and seasonal aquatic bed marshes and beaches are the major inshore fish habitats in St. Martins, Cedarville, Mackinac and Mismer Bays.

Larval Fishes

Larval seines, hand tows, boat tows and light-traps are effective for sampling bays.

Larvae are most abundant and speciose in permanent marshes, but some taxa are found only in seasonal marsh and open water.

Ten families of larval fishes were identified, but available keys do not permit analysis of most larvae below the family level.

Breeding occurs in all habitats and differences in larval fish communities among bays are small.

Numbers of individuals in larval taxa common to every bay are too variable for analysis of cohort growth using size-frequency analysis.

The number of larval taxa and larval abundance are more strongly affected by habitat diversity due to macrophyte composition than human impacts due to development.

Human development appears to have some impact on cyprinid representation.

The ichthyofauna in permanent marsh is more speciose and abundant, and more susceptible to impacts from human development.

Human development is believed to have its greatest impact through loss of marsh area and boat traffic.

The small number of useful larval taxa, variation in capture rates, laboratory facilities and expertise in identification suggests that although larvae are critical links in fish communities, they are not suitable for a monitoring or rapid assessment program managed by non-experts.

Juvenile/Adult Fishes

Gill nets, seines, electroshocking, Fyke nets and minnow traps are effective methods for fish collection. Seines are limited to beach areas with little Scirpus growth. Electroshocking is not considered effective in the shallow marsh areas. Gill nets are useful in seasonal and open-water habitat. Fyke nets are most effective in marshes.

Differences among bays can be detected using minnow traps.

Richness and abundances peak in June-July.

Compared to other degraded Great Lakes marshes, juvenile and adult fish communities are in good condition.

Although differences are found in growth rates of fish from different marshes, this variation occurs in early years only and may be attributed to gear bias.

As with larvae, numbers of individuals in species common to every bay are too variable for analysis of cohort growth using size-frequency analysis.

The ichthyofauna in permanent marsh is more speciose and abundant, and more susceptible to impacts from human development.

Cedarville Bay shows species losses, especially among cyprinids, lower abundance, and higher densities of fish characteristic of degraded habitat than other bays, and these are correlated with several measures of human development.

Mackinac Bay, although having much less human development than Cedarville Bay, shows some of the same trends, notably loss of cyprinids, suggesting changes in this group may provide early warning of marsh degradation.

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