Mortality Components in Fisheries Management
This content explores the various components of mortality in fisheries, including natural mortality, fishing mortality, recruitment, population numbers, and immigration/emigration. It discusses the definitions of instantaneous models, discrete and continuous fishery types, and the challenges in estimating natural mortality. The importance of controlling fishing mortality in fisheries management strategies is highlighted, along with discussions on estimating natural mortality values and catch curves.
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Presentation Transcript
Components of Z Natural Mortality Recruitment Population Numbers Fishing Mortality Immigration Emigration
Definitions Instantaneous Models F = instantaneous fishing mortality M = instantaneous natural mortality Z = F + M 6 Mortality Components
Definitions Discrete (Type I) Fishery F and M operate separately (different times) Realistic for a highly seasonal fishery 7 Mortality Components
Definitions Continuous (Type II) Fishery F and M operate at same time We will assume constant F & M through year 8 Mortality Components
Mortality Components As a manager, which of natural or fishing mortality can you control and, thus, want to know? Controlling F, u, m is a major goal of most fisheries management strategies. Very difficult to estimate precisely
Estimating M Assume a constant value for M Typically use M=0.2 Is this realistic? 12 Mortality Components
Estimating M Assume a constant value for M Relationship of M to life history traits See page 217 in IFAR 13 Mortality Components
Estimating M 14 Catch Curves
Estimating M 15 Catch Curves
