Determining stream origin and migration of four purported walleye stocks in Lake Erie using otolith elemental analysis.
Jennell Bigrigg, M.S. Student, D. Derek Aday (North Carolina State University), and Roy. A. Stein. Funded by: Ohio Department of Natural Resources, Division of Wildlife, Federal Aid in Sport Fish Restoration.

Understanding how fish populations are structured into stocks, as well as how stock movements drive distribution and abundance, is critically important to successful management of a fishery. Simply knowing that populations are divided into genetically identifiable spawning stocks can dictate a need for additional information, such as their relative productivity, distribution, and vulnerability to exploitation by humans. Clearly, if harvest occurs while stocks are mixed, then knowing the relative contribution of each stock to this harvest would be extremely valuable. With differential contributions to the harvest comes the opportunity for managers to exploit productive stocks and protect less productive ones, but only if they can differentiate stocks and anticipate their distribution and abundance in the environment. Consequently, knowing both origin and movement of the individual stocks of an exploited species is critical to effective management.

In this project, we seek to:

1) Identify and compare natal origin to subsequent spawning locations (Sandusky, Maumee, Grand rivers and open-water reefs) from otolith microchemistry of spawning adult walleye (year classes 1998 - 2002) to evaluate homing behavior in Lake Erie.

2) Determine migration of various walleye age classes in Lake Erie using otolith microchemistry.

3) Conduct a mixed stock analysis of age 1+ walleye to determine relative contribution of different spawning stocks to the Lake Erie walleye population.

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Jennell Bigrigg can be emailed at bigrigg.1 "at" osu.edu

Jennell displaying a walleye collected via shocking the Maumee River in March, 2004.

A pair of walleye sagittal otoliths, the one on
the left in resin and to be sectioned.

Otoliths are positioned in individual cells in a mold,
covered in resin, and placed in an oven to dry.

To quantify walleye spawning behavior, we are using laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS). Elemental concentrations (i.e. Sr, Ba, Mn, Mg, and Ca) across the otolith will be analyzed and compared to the unique elemental signatures of the above watersheds. With this information, we will be able to determine homing behavior, migration, and potentially, the relative contribution of these different spawning stocks.