This analysis of the variations of brown tiger prawn (Penaeus esculentus) catch in the Moreton Bay multispecies trawl fishery estimated catchability using a delay difference model. It integrated several factors responsible for variations in catchability: targeting of fishing effort, increasing fishing power and changing availability. An analysis of covariance was used to define fishing events t...

We used Monte Carlo simulations to evaluate how different methods of estimating fishery catchability within statistical catch-at-age analysis (SCA) performed when fishery catchability changed over time. Data-generating models included cases where catchability changed abruptly or gradually over time and where catchability was explicitly a function of population abundance, and we considered corre...

To estimate absolute abundance from research trawl surveys, the catchability of the fish to the gear must be known or estimated. Using 47 data sets of length-specific catchability, we conducted a hierarchical Bayesian metaanalysis of length-specific catchability for a number of different species groups. It was found that the Bayesian estimates of catchability were seldom near or above 1 for any...

I quantify the effects of 11 variables on the catchability of pelagic longlines, which are used to catch tunas and billfishes in the open ocean. Extension of the depth range and the duration of longline operations have reduced the catchability of several epipelagic species, such as mako sharks (Isurus spp.), since industrial longlining commenced in the tropical Pacific Ocean in the early 1950s....

This paper examines the correlation between biomass and catchability (q) of yellowfin tuna and the NAO index. Biomass estimates are obtained from a biomass dynamic model fitted to catch and cpue for the period 1950-1999. Several assessment scenarios are investigated. Scenarios are defined by the combination of indices used in the biomass dynamic model and the assumptions made about the variance...

I discuss the current approach to setting weighting factors (lambdas) for different types of information that contribute to the objective function when estimating parameters for Lake Erie percid stock assessments, and a suggested modification based on information indicating that catchability may be density dependent. This white paper was prepared in response to concerns that density dependent c...

The natural mortality (M) and purse-seine catchability and selectivity were estimated for Trachurus novaezelandiae, Richardson, 1843 (yellowtail scad)-a small inshore pelagic species harvested off south-eastern Australia. Hazard functions were applied to two decades of data describing catches (mostly stable at a mean +- SE of 315 +- 14 t p.a.) and effort (declining from a maximum of 2289 to 642...

The purpose of this paper is to study the coalition game between the potential fishing nations of Norwegian spring-spawning herring. We study a three-player cooperative game using Shapley value and nucleolus as solution concepts. We show that full cooperation between all fishing nations is not stable when the fishing fleets have a high-catchability coefficient. Further, the potential new member...

to estimate the fish composition and catchability coefficient of gillnet, a survey was carried out during april 2011 to march 2012 in the shadegan wetland, khuzestan province, iran. samples were collected from five stations viz., mahshar, rogbe, khorosy, ‍salmane and atish. approximately 4300 fish specimens were measured and depletion method was used for the estimation of catchability coefficie...