An Evaluation of the Selectivity Characteristics of Different Juvenile Fish Escape Panel Designs for the Demersal Trap Fishery of Abu Dhabi, United Arab Emirates

Abstract

The selectivity characteristics of 4 juvenile fish escape panel designs and their utility for the regulation of a multi-species demersal trap fishery were evaluated using a suite of objective socio-economic and biological criteria. The panel designs consisted of a control (type A) which had a hexagonal mesh size which was the same as that of the body of the trap (3.5 cm), a rectangular mesh (type B) which was representative of the current regulation (5.0 × 7.6 cm) and 2 escape panels with square meshes of 7.5 × 7.5 cm (type C) and 10.0 × 10.0 cm (type D). The results demonstrated that there was only a limited reduction in the proportion of juvenile fish and by-catch retained for the existing juvenile escape panel design (type B). Furthermore, as the selectivity characteristics for the key species (Epinephelus coioides and Diagramma pictum) were similar to the control type, the predicted increases in yields, revenues and spawning stock biomass were small by comparison. The escape panel with the largest mesh size (type D) retained the least un-utilized and discarded by-catch. Whilst simulations predicted the highest spawner biomass per recruit, long term yields and revenues for the key species, its use was associated with a dramatic short-term decline in revenues which were 23.3% of the value of the control type. Traps fitted with the type C which had a square mesh of 7.5 × 7.5 cm had the lowest juvenile retention and the highest overall score for all the assessment criteria combined. The study provides an empirical basis for gear regulations for the demersal trap fishery of the Emirate of Abu Dhabi and the wider Arabian Gulf region.

Gargoortrap fishery in Kuwait, catch rate and species composition

“…Simulated yield‐per‐recruit for hamoor and the haemulid Diagramma pictum showed increases in mean size as well as size at first capture with the largest panel mesh, i.e., 10 × 10 cm. The largest size panel mesh also resulted in the greatest long‐term improvement in spawner biomass per recruit, which was predicted to be 398% and 258% greater for E. coioides and D. pictum , respectively, over the control 3.8 cm mesh (Grandcourt et al, ).…”

“…Gargoor trials that tested four different mesh sizes [3.5 cm hexagonal (control), 7.6 × 5 cm, 7.5 × 7.5 cm, and 10 × 10 cm] of escape panels in Abu Dhabi, Arabian Gulf, had somewhat mixed results. The 7.5 × 7.5 cm mesh in the escape panel retained the lowest proportion of juveniles of key commercial species, whereas the 10 × 10 cm mesh retained the least by‐catch species (Grandcourt, Al Abdessalaam, Hartmann, Al Shamsi, & Francis, ). Simulated yield‐per‐recruit for hamoor and the haemulid Diagramma pictum showed increases in mean size as well as size at first capture with the largest panel mesh, i.e., 10 × 10 cm.…”

“…So there is no simple straightforward solution to improve landings without some negative aspects. Grandcourt et al () stated “that at existing fishing mortality rates, resource management targets of stock rebuilding cannot be achieved for the key species using gear regulations alone” for the tested escape panel designs. They concluded that a reduction in fishing effort is required.…”

Assessment of the Selective Properties and Optimization of Mesh Size of Pelagic Trawl Codends, Used for Fishing Mackerel (Trachurus Spp) in the Gulf of Guinea

“…These could be biological or biometric, physic-technical, technical and exploitation [24]. In this work, we just need to examine the influence of the meshsize which is an easily modifiable technical factor, and which, according to many papers presented on this subject-matter, has the most significant influence on the selective properties of trawl codends [25]. In fact, increasing the mesh size causes a displacement of the curve toward the right (Figure 1).…”

Trap modification opens new gates to achieve sustainable coral reef fisheries

“…The use of escape panels on demersal commercial trap fisheries has been studied (Stewart and Ferrell, ; Grandcourt et al ., , ), but the inclusion of escape gaps in coral reef traditional fish traps has received limited investigation and implementation. Some early efforts in heavily fished Caribbean coral reefs suggest promising results as traps retrofitted with rectangular escape gaps caught significantly fewer bycatch fish and were effective in releasing undersized individuals without significantly decrease the catchability of target species (Munro et al ., ; Johnson, ).…”