
%0 Journal Article
%A Francis, R. I. C. Chris 
%T Optimum design for catch sampling of eels
%J Marine and Freshwater Research
%D 1999/05/07
%V 50
%N 4
%P 343-353
%K 
%R https://doi.org/10.1071/MF98147
%U https://www.publish.csiro.au/paper/MF98147 
%X Data from the first two seasons of a catch-sampling programme for New Zealand freshwater eels (Anguilla australis and A. diefenbachii) are described. These are used in two simulation experiments to provide information to optimize future sampling. Results are presented in the form of equations that predict the precision of estimates (of species composition, mean size, and mean age at two different sizes) as a function of various survey design variables. Precision typically depends more on the number of landings (catches) that are sampled than the number of eels sampled per landing. Also, the precision obtainable from a given design varies substantially from fishery to fishery. For example, if 50 eels were measured and 10 otoliths collected from each of five landings, estimated standard errors varied by a factor of 9 for species composition, 19 for mean weight, and 5 for mean age at the minimum legal size, depending on which fishery was sampled. Results for mean age estimates are more restricted and less certain (than those for species composition and mean size) because age data were fewer. Three further optimization issues are discussed: sampling costs, the importance of &#8216;minor&#8217; species, and the pool of fishers from which samples are collected. 
