The major objectives of this project are to determine the variability in trace element contents of white bass otoliths and to better understand the causes (geochemical and biological) of this variability, so that stocks can be identified and migration patterns can be determined. We propose to do this through temporally and spatially explicit sampling of larval, juvenile, and adult white bass in western Lake Erie, as well as conducting a novel enclosure experiment in Lake Erie. The specific goals of this project are:
to establish a statistically discriminate trace element pattern for different spawning sites (rivers and reefs) in light of measured temporal variability.
to determine the temporal consistency of chemical spawning site signatures (i.e., between years).
to determine the degree of philopatry of white bass in western Lake Erie.
to assess the degree of coherency of migration of white bass stocks in western Lake Erie (i.e., do stocks use different water bodies?).
to determine the consistency of small- and large-scale patterns in otolith chemical signatures from fish restricted to specific locations (e.g., how variable is otolith microchemistry of white bass juveniles from different locations within Maumee and Sandusky bays?). The specific tasks proposed to achieve our stated goals are:
The specific tasks proposed to achieve our stated goals are:

1. to measure (using laser ablation ICPMS) and compare otolith trace element signatures in a statistically significant number of spawning adult fish (N≥40 per site) collected from the four prominent spawning sites in western Lake Erie (Sandusky and Maumee rivers, southern reef system, and from Canadian waters). Data will be collected at high spatial resolution (to <10 m for Sr and Ba analysis) across the entire otolith (core to rim) and along specific bands parallel to the annuli/rim in order to establish timing and patterns of migration, changes in habitat use, and to identify natal sites of individuals and groups. Repeat surveys will be performed each year to evaluate temporal variability of the trace element signature.
2. to measure and compare trace element chemistry of otoliths of larval white bass versus the rim region of otoliths from spawning adults caught at the same time, and the core region of otoliths from spawning two-year old adults collected two years later. We will attempt to establish a temporally-resolved natal signature in order to evaluate adults in later collections and to assess whether adult fish (male and female) acquire a measurable site signature during spawning.
3. to place early juvenile white bass in enclosures in different locales in western Lake Erie (selected in part by differences in water chemistry) to evaluate the degree of variation in chemical signature across spatial scales and the degree of seasonal (i.e., temporal) variability in water chemistry in a given locale as reflected in otolith microchemistry and water samples.
4. to measure and compare the trace element signature of otoliths of larval white bass from spawning sites with those of juveniles obtained during fall survey collections in different regions of western Lake Erie to determine percentage of total population coming from each spawning stock.

Beyond the specific scientific goals, an important objective of this study is to provide training for graduate and undergraduate researchers to provide highly skilled graduates to fill the need for environmentally focused scientists in the workforce. To this end, support is requested for both graduate and undergraduate students who will perform most of the research under the mentorship of the principle investigators.

Understanding the extent to which a fishery consists of discernable stocks is vital for effective fisheries management. For example, if different breeding stocks exist, then managers have the potential to individually manage these stocks, enabling exploitation of healthy stocks and implementation of restoration strategies to protect overexploited or environmentally impaired resources. Likewise, the ability to assess habitat use, the degree of migration coherency, the degree of mixing of breeding stocks, and the degree of philopatry of fish are critical to developing and monitoring effective fish management strategies.

The recent advances in the analysis of otolith microchemistry provide a powerful means to identify spawning sites and to track dispersal and retention of fish throughout ontogeny. The approach yields both spatial and temporal information on fish dispersal and movement. The otolith composition studies also provide valuable information on patterns of migration and habitat use, thereby providing a means to evaluate points of intersection between fish populations and human activities (i.e., to discriminate stocks).

Trace element abundance in the otoliths will be determined using laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS). The approach is based upon the observation that elemental abundance in fish otoliths are directly and predictably related to the chemistry of the water in which they grew. Recent advances in the analytical tools to be employed yield high precision data that can be spatially correlated with the annular structure in the otoliths, thus providing a chronologically correlated record of changes in water chemistry (ie, habitat) throughout the fish's lifetime. Most of the methods have been successfully tested through a development grant.

Spawning adult white bass will be collected from the Maumee, Sandusky and Detroit rivers and at least two reef sites in the spring of each year. The collection will involve electroshocking, and collection of angler harvest. We will collect 15-20 fish of each sex from each location without regard to fish size or age, although these variables will be determined. Larval fish will be collected using an ichthyoplankton net. The caging incubation study will be conducted by introducing larval white bass into small enclosures (1m³ with 500-mm mesh), periodically inoculating cages with ambient zooplankton and allowing fish to grow to sufficient size (e.g. 25-30 mm or larger with shifts in cage dimensions) to then conduct analyses to obtain the elemental signatures.