Performance of a Square Mesh Panel in Capturing Immature Indian Halibut in Shrimp Trawlers in the Persian Gulf

Abstract The performance of a square mesh panel (90 mm stretched mesh size) on reducing the catch of immature Psettodes erumei Bloch and Schneider, 1801 smaller than Lm50% value was tested in a small-scale shrimp-trawl fishery along Hormuzgan coasts in the The Persian Gulf. During shrimp season, 25 trawl hauls were carried out and a total of 371 P.erumei was caught in the codend and cover net. Length ranges of Indian halibut caught in the codend and cover net were 8-35.2 cm and 9-25 cm and their mean lengths were 24.58±5.8 cm and 15.29±3.5 cm, respectively. Two sample Kolmogorov-Smirnov tests detected significant difference in the sizefrequency distribution of P.erumei between codend and codend plus cover net (Dks= 2.464; P< 0.001). The results of two-sample t-tests detected a significant difference (P<0.001) in the mean length of P.erumei caught in the codend and cover net. The escape rate, based on number was 28.8%. The length of 50% retention (L50) was 17.2 cm and differed greatly from the Lm50% (37.3 cm). The square mesh panel efficiency was not so acceptable. An increase in mesh size of codend or mesh size of square mesh panel during shrimp fishing season will be required to delay capture until fish is reached Lm50% and Lm value. It is more likely that samples of immature Indian halibut were influenced by the spatial and temporal distribution of the species as well as mesh size of panel, weak swimming capability of P.erumei and body form of species

Estudio comparativo de pesca pelágica recreativa entre las artes de línea de mano y curricán en el golfo de Omán, Irán

The choice of fishing gear and catching strategy should be taken into consideration in the management of fish stocks. Here, paired fishing trials in a pelagic recreational fishery compared the catch composition, catch rate and size selectivity between handline and trolling fishing methods in Iranian coastal waters of the Gulf of Oman. Total catch rate was 1.06 fish hr–1 vs 0.88 fish hr–1 for handline and trolling, respectively, a 17% difference which was significant (p < 0.05). Generally, the handline method captured more fish than trolling for most species, but size selectivity tended to be species-specific per gear type. The handline fishing method captured larger talang queenfish (Scomberoides commersonnianus), while trolling captured larger narrow-barred Spanish mackerel (Scomberomorus commerson), pickhandle barracuda (Sphyraena jello) and Indian threadfish (Alectis indicus). Technical measures, such as gear restrictions, could be applied to recreational pelagic fisheries management in the Gulf of Oman. Such measures could improve species-specific exploitation patterns.La selección del equipo de pesca y la estrategia de captura deben ser consideradas en la gestión de stocks pesqueros. En el presente estudio se muestran resultados de tipos, tasas y selectividad de talla de las capturas en una experiencia comparativa de artes de pesca en aguas costeras del golfo de Omán, Irán. Las tasas de captura finales para las artes de línea de mano y curricán fueron de 1.06 y 0.88 peces h–1 respectivamente, mostrando un significativo 17% de diferencia entre ambas (p < 0.05). Por lo general, el arte de línea de mano resultó en una mayor tasa de captura multiespecífica, sin embargo la selectividad de talla se observó arte-dependiente. En el arte de línea de mano se observaron capturas de mayor talla para la especie “talag queenfish” (Scomberoides commersonnianus), mientras que para el curricán fueron la caballa o verdel (Scomberomorus commerson), barracuda (Sphyraena jello), e “Indian threadfish” (Alectis indicus). En conclusión, la implementación de medidas técnicas, como restricciones en las artes de pesca, podrían ser aplicadas en la regulación de la normativa de pesca recreativa para la gestión general pesquera con el objetivo de la mejora en los patrones de explotación especie-específica del golfo de Omán

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

Study on different hook and bait types in the Persian Gulf hand line fishery: optimization and development

The hand line fishery in the Persian Gulf is considered a sustainable fishing practice. The aims of this study were to estimate catch composition, catch rates, length frequencies, and the percentage of individuals caught below length-at-maturity with two types of hooks, circle and J-style with natural and artificial bait by hand line fishing. Circle and J-style hooks with natural and artificial bait were alternated. Sampling operations were carried out on Qeshm Island, in the North of the Persian Gulf in spring 2015. Catch per unit effort for J-hooks with natural and artificial bait and circle hooks with natural and artificial bait differed significantly (p  0.05). For most species (except L. nebulosus), there was no significant difference between circle and J-style hooks for the proportion of individuals smaller than length-at-maturity (p > 0.05)

Mono-vs multifilament gillnets: effects on selectivity of narrow-barred Spanish mackerel Scomberomorus commerson in the Persian Gulf

Iranian coastal fishers targeting narrow-barred Spanish mackerel (Scomberomorus commerson) recently replaced their historical multifilament gillnets with those made from monofilament, evoking management concerns over potential increases in catch-per-unit-of-effort. During 20 fishing days, we compared catches from replicate surface-set gillnets that were identical in terms of mesh size (140 mm stretched opening), length (180 m), depth (30 m), hanging ratio (0.56) and spatiooral deployment, but had different materials: Multifilament (1.8-mm diameter twisted twine) vs monofilament (0.8-mm diameter twine). Compared with the multifilament gillnet, there was a trend of greater catches (up to 1.3×) of S. commerson and another retained species, mackerel tuna (Euthnus affinis), along with one discarded species, giant catfish (Netuma thalassina) by the monofilament gillnet. However, statistical significance was restricted to E. affinis catches and a bias towards smaller S. commerson. These differences were attributed to species-specific catching mechanisms within gillnet material, with larger S. commerson retained by their teeth in the multifilament and all E. affinis more securely retained by their deeper bodies in the monofilament. Gillnet materials require regulation to preclude excessive effort on fully exploited stocks of species such as S. commerson

Understanding fishery interactions and stock trajectory of yellowfin tuna exploited by Iranian fisheries in the Sea of Oman

The predominant policy for remedying the world fishing crisis aims at maximum sustainable yield (MSY) by adjusting gear selectivity and fishing effort to maintain sustainable stock levels. The yellowfin tuna (Thunnus albacares) fishery in the Sea of Oman has experienced intense increases in removals since 1980, with particularly high levels since the 1990s. Here, we apply a statistical catch-at-age model to time-series of catches and fishery-dependent length composition data to obtain a preliminary and general understanding of the population dynamics of this stock since the start of the fishery in 1950–2019. Despite limited data, population models consistently indicate a sharp decline in population status since the beginning of the time-series across a variety of assumptions on stock productivity and life history. The gillnet fishery takes almost exclusively immature individuals, with high fishing intensity and removal rates. Both reference models indicate the population is essentially at the same relative stock status in 2019 (10% of unfished), but with very different future projections and higher absolute stock size when recruitment is estimated. The yellowfin tuna population in 2019 is below estimated MSY reference points (based either on unfished size or spawning output at MSY) for current relative stock size, and over the fishing intensity at MSY, indicating current overfishing. Adjusting the interactions of that fishery with the population, while continuing to collected biological composition data representative of each fleet in the fishery, will help mitigate current stock decline and provide the ability to refine future population status determination and forecasts through more informed stock assessments