mortality Flashcards
to analyze tropical species mortality rates, the age of the fish is substituted with what?
the length
what life history parameters are used to estimate mortality?
- von Bertalanffy growth coefficient K
- age and size at maturity
- maximum age of different species among others
- maximum size of a species
Name 2 indirect and 3 direct methods of estimating mortality rates
I:-life history parameter estimates -Beverton-Holt equations D: catch curves (age based) -catch curves (length based) -mark recapture methods
what do the following symbols represent? Z F M S A
Z=total instantaneous mortality rate
F= instantaneous mortality rate due to fishing
M=instantaneous mortality rate due to natural causes
S=discrete survival rate
A= discrete mortality rate
what is the usual form of expression for mortality? (as in equation)
instantaneous mortality rates
what is GSI?
gonadosomatic index,
a ratio between the wet wight of a fish’s gonad and the wet weight of its body, less the gonad removed, and the stomach contents flushed out
who invented GSI?
Gunderson and Dygerts method
Hoenig’s method estimates total or natural mortality?
total, unlike G&D’s method and Pauly’s Method
What is unique about Hoenig’s method?
it can be used for stocks other than fish
what is perhaps the best known method of calculating mortality rates in fish that can be accurately and reliably aged?
Age based catch curves
what sort of catch curve would you use in a tropical area?
length based catch curve
N
number of fish (actual or biomass)
Nt
Number of fish at a time
Ninf
Number of fish in a virgin unfished population
CPUE
Catch per unit of effort
