The IPHC requests your help as we design and implement a sampling program to determine the sex of halibut that are landed by the commercial longline fishery. Accurate sex-ratio information is necessary for stock assessment - most notably, for accurately estimating and monitoring spawning stock biomass.
We rely on random sampling so that the data we collect are representative of the entire catch. Just like our otolith sampling, we cannot add samples outside our normal frame without creating bias. You still get hats though (and maybe a jacket)! An important part of this year’s study is testing the marking procedure. Please provide feedback to your port sampler regarding how it went.
The most informative data comes from the sex-ratio at age, and to get that we need a mark on every fish for which we collect a length, weight, and otolith. If you can guess which of your fish will be selected for otolith sampling, then just mark those.
We would know that the marked fish were males; but we couldn’t be sure that all of the unmarked fish were females. Mistakes happen, and some fish will surely go unmarked. If only the males were marked, then every “mistake” would become a female even if had been a male. The result would be a sex ratio that is mistakenly biased towards females (or, if only the females were marked, biased towards males). By marking both sexes, the sex ratios estimated from the markings should – on average – be correct even if a small number of fish slip through the process unmarked.
The commercial catch is removed from the population, and we need to know its properties to estimate the impact of these removals on the stock. It is also quite likely that the fishery is encountering males and females in different proportions in the spring and fall, when we have no survey data.
If you have an unanswered question, please contact Tim Loher.
Nearly all of the research done by the IPHC staff is directed toward one of three continuing objectives of the Commission: i) improving the annual stock assessment and quota recommendations; ii) developing information on current management issues; and iii) adding to knowledge of the biology and life history of halibut. In each of these areas our work program applies the best information and methods available, and our research program aims to improve the information and methods by answering the most important outstanding questions.