On improving operation and use of the elefan programs. part 3, correcting length-frequency data for the effects of gear selection and/or incomplete recruitment uri icon

abstract

  • One important feature of lengthâ??frequency data that is usually ignored when data are collected for subsequent estimation of growth and various related parameter estimates is that lengthâ??frequency data are necessarily collected with gears that are always selective for certain sizes. This feature often results in lengthâ??frequency samples that cannot be used to extract growth and mortality parameter estimates, for example in the case of data sampled by means of a gillnet. On the other hand, it is usually possible to extract growth and mortality parameter estimates from lengthâ??frequency data obtained using trawls, Danish seines and similar gears. These estimates will usually be biased, however, because of some residual selection and other effects. A method is presented here which allows for a partial correction of such biases, as related to the estimation of growth parameters (L. and K) using the ELEFAN I program

publication date

  • 2011