Geology topics

Neal Godby

Publications and source records attributed to Neal Godby.

3 recordsLinked to original sources

USGS2025

Water temperature analysis of the North Branch Au Sable River, Michigan, and implications to salmonid populations

Ambient stream water temperatures affect salmonid movement and survival with fish actively seeking thermal refugia from warming waters. This study sought to investigate the potential role of water temperature in the perceived decline in native Brook Trout Salvelinus fontinalis and non-native Brown Trout Salmo trutta populations in the North Branch Au Sable River by fishers and reported to resource managers in 2018 and 2019. Water temperature was analyzed at nine stations within the North Branch Au Sable River in 2021 and 2022. A total of 61,390 temperature observations were collected with 58.0% exceeding the optimal growth threshold for Brook Trout of 16°C; 37.9% exceeding the movement threshold for Brook Trout of 18°C; 3.4% exceeding the upper limit for positive growth for Brook Trout of 23.4°C; and 28.6% exceeding the optimal growth threshold for Brown Trout of 19°C. The maximum daily water temperatures recorded for each year were 27.58°C in 2021 and 26.89°C in 2022. The availability of cold water thermal refugia is critical to the viability of native Brook Trout populations in the North Branch Au Sable River and its tributaries. Efforts should be taken to increase ambient stream water temperature monitoring year-round and to determine the size, frequency, and availability of thermal refugia within the watershed to increase the likelihood of a system resilient to the impacts of a warming climate.

Michigan↗

USGS2014

Designing long-term fish community assessments in connecting channels: Lessons from the Saint Marys River

Long-term surveys are useful in understanding trends in connecting channel fish communities; a gill net assessment in the Saint Marys River performed periodically since 1975 is the most comprehensive connecting channels sampling program within the Laurentian Great Lakes. We assessed efficiency of that survey, with intent to inform development of assessments at other connecting channels. We evaluated trends in community composition, effort versus estimates of species richness, ability to detect abundance changes for four species, and effects of subsampling yellow perch catches on size and age-structure metrics. Efficiency analysis revealed low power to detect changes in species abundance, whereas reduced effort could be considered to index species richness. Subsampling simulations indicated that subsampling would have allowed reliable estimates of yellow perch ( Perca flavescens ) population structure, while greatly reducing the number of fish that were assigned ages. Analyses of statistical power and efficiency of current sampling protocols are useful for managers collecting and using these types of data as well as for the development of new monitoring programs. Our approach provides insight into whether survey goals and objectives were being attained and can help evaluate ability of surveys to answer novel questions that arise as management strategies are refined.

Saint Marys River↗

USGS2011

Long-term trends in the St. Marys River open water fish community

We examined trends in species composition and abundance of the St. Marys River fish community. Abundance data were available approximately once every six years from 1975 through 2006, and size and age data were available from 1995 through 2006. We also compared survey data in 2006 with results of a concurrent creel survey that year, as well as data from prior surveys spanning a 69 year time frame. The St. Marys River fish community was best characterized as a coolwater fish community with apparent little variation in species composition, and only slight variation in overall fish abundance since 1975. However, we did find recent trends in abundance among target species sought by anglers: centrarchids increased, percids appeared stable, and both northern pike Esox lucius and cisco Coregonus artedii declined. Survey results suggested that walleye ( Sander vitreus ) and yellow perch ( Perca flavescens ) experienced moderate exploitation but benefited from recent strong recruitment and faster growth. Mechanisms underlying declines of northern pike and cisco were not clear; reduced abundance could have resulted from high exploitation, variation in recruitment, or a combination of both factors. Despite these challenges, the St. Marys River fish community appears remarkably stable. We suggest that managers insure that creel surveys occur simultaneously with assessments, but periodic gill net surveys may no longer provide adequate data in support of recent, more complex management objectives. While additional surveys would add costs, more frequent data might ensure sustainability of a unique fish community that supports a large proportion of angler effort on Lake Huron.

Michigan;Ontario↗