Status of Lake Trout in the Main Basin of Lake Huron: A Summary of (SCAA) Models and Projections
Aaron Woldt--MDNR Alpena
Lake Huron lake trout stocks crashed due to overfishing and mortality due to sea lamprey in the 1940’s
Rehabilitation efforts started in the 1970’s and consisted primarily of:
Lake trout stocks are monitored annually by MDNR, CORA, USGS BRD, OMNR, and USFWS
We developed 2 types of models
1) SCAA model--uses user supplied inputs and iteratively solves for population parameters like M, F, Z, abundance, SSB….
2) Projection model--uses last year’s output from SCAA model to predict population parameters into the future (2020 in our case).
Also allows user to alter projection parameters (i.e. effort).
Inputs to SCAA model
Stocking (w/ movement matrix)
Commercial fishery effort and yield (state licensed, tribal, and Canadian) from LMGN, SMGN, and trap nets
Recreational fishery effort and harvest
Commercial and recreational harvest age compositions
Mean weight of lake trout harvested by each gear (LMGN, SMGN, trap net)
Inputs to SCAA model (cont.)
Estimate of under-reporting or discards
Survey catch, CPE, and age compositions
Estimate of natural mortality
Estimate of sea lamprey mortality rates at age by year
Estimate of trap net by-catch mortality
Estimate of lake trout weight at age
Estimate of lake trout maturity at age
Estimate of fecundity
N. L. Huron Projection Scenarios
CPE of YOY lake trout at North Point Thunder Bay
N.C. L. Huron Projection Scenarios
Estimated lake trout sport catch, Michigan waters of Lake Huron
1) The management strategy now in place in the main basin of Lake Huron may allow for the rehabilitation of lake trout stocks by 2020.
2) Control of sea lamprey and fishing mortality is necessary for rehabilitation to progress.
3) Cooperative management between USA, 1836 tribes, and Canada is needed to control lake trout mortality in the main basin of Lake Huron.
4) The modeling subcommittee of the Technical Fisheries Committee will update the SCAA models yearly to set TAC’s and monitor progress towards rehabilitation.