By Jeff Wyatt and Robin English
The Seneca Park Zoo’s Conservation Plan prioritizes Lake Ontario and Genesee River ecosystem health through leadership and alliances developing and supporting species recovery, habitat restoration, applied research and public awareness programs. The lake sturgeon (Acipenser fulvescens), extirpated from Rochester’s waterways before 1930, now has a second chance to swim the Genesee River due to the success of a community education and sturgeon reintroduction program conducted by the Seneca Park Zoo, U.S. Geological Survey (USGS), the U.S. Fish & Wildlife Service (USFWS) and the N.Y.S. Department of Environmental Conservation (NYSDEC). This largest indigenous freshwater fish of the Great Lakes thrived for 10,000 years until the mid- to late 1800s when their economic importance was recognized. Intensive commercial exploitation of sturgeon, coupled with habitat fragmentation and degradation caused a dramatic decline resulting in only remnant populations.
The Genesee River, one of the major tributaries to Lake Ontario and part of the Rochester Embayment EPA Area of Concern (AOC), drains 6,400 km2 of diverse agricultural and highly urbanized areas. A significant improvement in water quality over the past twenty years and a 1999 assessment finding suitable habitat created an opportunity to consider the Genesee River as an excellent candidate for restoration of a self-sustaining lake sturgeon population through stocking. Additionally, the Rochester Embayment Remedial Action Plan emphasizes a ten-to-thirty year process evaluating biological indicators such as the lake sturgeon to set de-listing criteria for the EPA AOC. One delisting criterion will be met when lake sturgeon of all life stages inhabit the Genesee River. Ultimately, we hope through this collaborative project to promote environmental stewardship of the Greater Rochester watershed and waterways as we restore native fish communities and improve ecosystem health.
The Genesee River sturgeon reintroduction program began in early June 2003 and 2004 with gamete harvest from fish netted in the St. Lawrence River and primed with luteinizing hormone releasing hormone (LH-RH). The LH-RH treated adult sturgeon readily discharged large volumes of sperm and eggs from their vents during gentle manual restraint. Sperm activated in river water and eggs were mixed and subsequently treated in the field with Fuller’s Earth and iodophor as part of a de-adhesion and disinfection protocol. Fertilized eggs taken to NYS DEC fish hatcheries hatched after five-to-ten days of incubation. Fry progressed from eating zooplankton (e.g. daphnia) to brine shrimp and bloodworms as they grew over three months into 8 to 10 inch long fingerlings suitable for release. In the fall of 2003 and 2004, a total of 1,900 fingerling sturgeon were released from aerated live wells of USFWS and USGS boats in the Genesee River in sandy-silty, nursery habitat adjacent to Seneca Park Zoo.
A new zoo exhibit and docent programming highlights this signature conservation program displaying hatchery reared sturgeon in a 180 gallon chilled (62F) tank. Each exhibited fish is tagged in the dorsal fin demonstrating the same yellow, Floy™ spaghetti tag used to identify their Genesee River counterparts. These uniquely numbered tags provide local anglers with contact information for reporting accidental captures. The sturgeon exhibit graphics and programming off- and on-site heighten community awareness of the local reintroduction program and practical, day-to-day household activities designed to protect and restore regional watershed and waterway ecosystem health.
Mark and recapture gill net surveys conducted from September 2003 through August 2005 provided a Schnabel population estimate of 1,071 sturgeon still present in the river with habitat preferences of sites at 6 meters deep with gravel substrates abundant with shells of dead mollusks. The Summer 2008-2009 mark and recapture surveys demonstrated population estimates of 945-950 sturgeon remaining in the river with a pattern of movement northward and possibly out of the river into Lake Ontario. Length and weight data demonstrated growth rates similar to healthy, wild populations of sturgeon in Wisconsin (2003/2004 stock size of 210 & 169 mm and 44 & 23 grams, respectively increasing to 2009 survey measurements of 03/04 year class releases of 608 & 758 mm and 1.2 & 2.4 kg, respectively). The largest sturgeon captured in summer of 2009, measuring 972 mm and weighing 5.65 kg, increased 363% in length and 12,741% in weight from its 2003 year class average release measurements. Gastric lavage analyses of recaptured sturgeon identified a diet of nearly 99% Chironomid sp. midge larvae found in abundance on the Genesee River bottom during survey months.
The research results thus far support the hypothesis that the lower Genesee River contains habitat suitable for growth and survival of stocked juvenile sturgeon. The post-stocking river retention, growth and habitat use by the hatchery reared fish has validated sturgeon stocking as a sound conservation management tool in the Genesee River and likely in similar Great Lakes’ tributaries. Possible next research steps involve gill net surveying shallow areas of Lake Ontario beyond the mouth of the Genesee River, gastric lavage analyses to evaluate possible feeding on zebra mussels and radio or sonic tagging for tracking juvenile sturgeon movements into Lake Ontario. The 2003/2004 reintroduced sturgeon will not re-enter the Genesee River from Lake Ontario for spawning until 2020 when the females may first reach sexual maturity at an age ranging from 16-to-33 years. The longevity (55 years for males and 80-150 years for females), slow adult growth rate, late age of sexual maturity and intermittent spawning, (4-to-9 year intervals), continue to make the lake sturgeon extremely vulnerable to over fishing and degradation & fragmentation of spawning & feeding habitat. The promising findings of our sturgeon reintroduction project in the Genesee provide a start towards meeting the sturgeon-based delisting criteria for the Rochester embayment Area of Concern. The timeframe for study of restoration of a self-sustaining lake sturgeon population in the Greater Rochester area is likely longer than the research career of individual scientists. We hope our initial success will inspire community stakeholders, families and scientists to continue protecting habitat and safeguarding sturgeon as they return to the Genesee River to spawn for centuries to come.
Jeff Wyatt DVM, MPH, DACLAM- Director of Animal Health & Conservation Science - Seneca Park Zoo
Robin English BS- Hospital Keeper, Seneca Park Zoo
Dawn E. Dittman PhD, USGS Research Ecologist, Tunison Laboratory of Aquatic Science, Cortland, NY