Evaluation of Sampling Techniques for Age-0 Lake Sturgeon in a Lake Michigan Tributary

Abstract

Rehabilitation of lake sturgeon Acipenser fulvescens in the Great Lakes would benefit from a greater understanding of early life stage attributes. The objectives of this study were to determine the efficacy of active and passive sampling gears for capturing age-0 lake sturgeon and evaluate whether the most effective gear types were size selective. Fish were collected by means of active (i.e., wading, haul-seine, backpack electrofishing, snorkeling surveys, and bottom trawls) and passive (i.e., gill nets, set lines, and fyke nets) sampling gears from June to November of 2002 and 2003 in the lower Peshtigo River, Wisconsin, and nearshore waters of Green Bay. Mean catch per unit effort (CPUE) was greatest for day wading (0.036 fish/min), followed by day haul-seine surveys (0.029 fish/min), night wading (0.020 fish/min), and night haul-seine surveys (0.015 fish/min). Night wading surveys captured the greatest number of fish (N = 118). Day and night electrofishing (CPUE = 0.008 and 0.013 fish/min, respectively), snorkeling (CPUE = 0.010 fish/ min), and gill nets (CPUE = 0.026 fish/d) were less effective gear types, while bottom trawls, set lines, and fyke nets did not capture fish. Smaller fish were captured during day wading and haul-seine surveys (median = 71 and 68 mm, respectively) than during night wading and haul-seine surveys (median = 120 and 133 mm, respectively). Based on these results, we recommend the use of wading and haul-seine surveys to collect age-0 lake sturgeon in shallow lotic and lentic systems, such as the lower Peshtigo River and Green Bay, that are characterized by low current velocity and high water clarity.