Effect of hook and bait size on catch efficiency in the Persian Gulf recreational fisheries

The effect of hook and bait sizes on the catch efficiency and size composition of Spangled Emperor Lethrinus nebulosus, Orange‐spotted Grouper Epinephelus coioides, and Narrowbarred Mackerel Scomberomorus commerson was investigated in the recreational and semi‐subsistence handline fishery in the Persian Gulf. Based on expectations that increasing hook and bait sizes would decrease the catch efficiency of the smaller individuals while maintaining the catch efficiency of larger fish, we investigated the effect of increasing hook and bait sizes. For all three species, the results indicated slightly lower catch efficiency for the smaller fish when larger hooks were used. Furthermore, the results demonstrated a significant increase in catch efficiency for the larger sizes of Spangled Emperor and Orange‐spotted Grouper when fished with larger hooks, an effect that increased with fish size for both species. Additionally, the overall catch efficiency did not vary significantly when increasing hook and bait sizes for the three species investigated. This study shows that fishing with larger hooks and larger bait would change the exploitation pattern of these species toward higher proportions of larger fish in the catches. Moreover, based on the size distribution of the species on the fishing grounds during the study period, the use of larger hooks and bait would lead to significant increases in the total number of Spangled Emperor caught (41% increase; 95% confidence interval [CI] = 17–69%) and the total number of Orange‐spotted Grouper caught (151% increase; 95% CI = 132–336%), respectively. The results indicated a similar effect for Narrowbarred Mackerel; however, the effect was far less profound than for the two other species and was not significant for any size‐classes

Understanding and predicting size selection in diamond-mesh cod ends for danish seining: A study based on sea trials and computer simulations

Danish seining is an important fishing method used to harvest demersal species. Knowledge about the size selectivity of different demersal species with this type of fishing gear is therefore of importance for managing the exploitation of marine resources. However, there are only limited data on size selection in cod ends in this fishery. Sea trials were therefore carried out to collect size selectivity data for Atlantic Cod Gadus morhua, Haddock Melanogrammus aeglefinus, and Witch Flounder Glyptocephalus cynoglossus for a diamond-mesh cod end. For all three species, the data were best described by a double logistic selection curve, implying that two different size selection processes occur in the cod end. The double selection process could be explained by an additional selection process occurring through slack meshes. The results imply that the escapement of 46% and 34% of the larger Atlantic Cod and Haddock (those above 48 cm), respectively, would be through wide-open or slack meshes. Since these mesh states are only likely to be present in the latest stage of the fishing process (e.g., when the cod end is near the surface), a large fraction of the bigger fish probably escaped near the surface, which might influence their likelihood of survival. Furthermore, based on the models established for explaining the experimental size selection, we were able to predict the effect of changing the mesh size on cod end size selection in the Danish seine fishery

When is enough, enough? Quantifying trade-offs between information quality and sampling effort for fishing gear selectivity data

There is general pressure throughout the world’s fisheries for the industry to have greater involvement not only in the development of fishing gears but also in the testing and documentation of their effect. In the European Union, the Common Fisheries Policy of 2013, together with the proposed reform of the technical measures regulation, highlights the need for greater flexibility in fisheries through increased stakeholder involvement. To achieve this flexibility, there is a need for additional fishing gears available to the fishermen. A way to facilitate this is to have the industry take part in the development and testing of fishing gears, as well as collect data on their performance. However, to have a successful industry-collected data programme, fishermen have to be able to collect data on the length of a portion of the catch. In this study, we determine how many individuals need to be measured to correctly evaluate the relative selective performance of a new gear compared to a standard gear. The evaluation was carried out by analysing catch ratio curves, their associated uncertainties, and the trade-offs between uncertainties and sampling effort. Results show that with relatively small sample sizes (500 to 1000 individuals) it is possible to correctly evaluate the performance of a gear for a given species. By having the industry develop and test their own gears, as well as being involved in the collection of data, the number of potential gear solutions available to address the different issues emerging in the fisheries is increased