Estimating walleye (Sander vitreus) density, gear catchability, and mortality using three fishery-independent data sets for Oneida Lake, New York

• Published in: Canadian journal of fisheries and aquatic sciences 2008-07, Vol.65 (7), p.1366-1378
• Main Authors: Irwin, Brian J, Treska, Theodore J, Rudstam, Lars G, Sullivan, Patrick J, Jackson, James R, VanDeValk, Anthony J, Forney, John L
• Format: Article
• Language: English
• Subjects: Agnatha. Pisces; Animal populations; Animal, plant and microbial ecology; Applied ecology; Aquatic ecosystems; Biological and medical sciences; Death of; Exploitation and management of natural biological resources (hunting, fishing and exploited populations survey, etc.); Fish; Fisheries; Fishing nets; Freshwater; Fundamental and applied biological sciences. Psychology; Influence; Lakes; Methods; Mortality; Phalacrocorax auritus; Physiological aspects; Population density; Sander vitreus; Sensitivity analysis; Vertebrates: general zoology, morphology, phylogeny, systematics, cytogenetics, geographical distribution; Walleye (Fish); Walleye fishing
• ISSN: 0706-652X; 1205-7533
• DOI: 10.1139/F08-062

We used three long-term data sets (gill nets, trawls, and adult population estimates) for walleye ( Sander vitreus ) to simultaneously estimate density, gear catchabilities, and mortality using an age-structured, nonlinear model. Model constraints included a fixed natural mortality rate and age- and gear-specific but time-invariant catchabilities. Trawl catchability decreased with age, whereas gillnet catchability increased towards a maximum by age-4. A sensitivity analysis was conducted to investigate how the information content of the different data sets influenced parameter estimates. Estimated catchability values were relatively robust to changes in data weighting. Estimated gillnet catchability values were fairly consistent with those derived from more conventional methods. An additional mortality term was added to reflect double-crested cormorant ( Phalacrocorax auritus ) predation, and vulnerabilities associated with angling and cormorants were calculated using independent length frequency information. Estimated subadult mortality increased and the influence of fishing mortality slightly decreased during recent years when double-crested cormorants were abundant and more restrictive size limits were in place. Walleye density in Oneida Lake (New York, USA) in the last decade is estimated to be approximately half of that before 1990.