Factors Affecting Catchability in Longline Fishing of Red Grouper in the Southeastern Gulf of Mexico

Abstract

Catchability (q) is a key parameter in stock assessment that can vary in response to biological (e.g., abundance), spatial (e.g., fishing zones), and fishing technique and tactic (e.g., fishing gear design) factors. Few studies have been done on the influence of these sources of variation on q estimates. Catchability was calculated for Red Grouper Epinephelus morio caught with bottom longlines in two coastal zones fished by the small‐scale fleet in Yucatan, Mexico. Experimental data collected from these catches were used to assess the effect on q‐values of fishing zone and depth stratum, hook and bait size, and fish length. Three longlines were each equipped with one of three sizes (13/0, 14/0, or 15/0) of Mustad circle hooks. Bait was Atlantic Thread Herring Opisthonema oglinum in one of two sizes: 4 or 8 cm long. Sampling occurred in two zones (west and east coast) and in three depth strata (10–15 m, 15–20 m, and >20 m). Generalized linear models were used to identify any effect of the analyzed variables on q. Fishing depth and bait size alone had no apparent effect on q, but a combined effect of hook (14/0) size and bait (8 cm) size on q was observed. Fishing zone, hook size, and fish total length were significant sources of variation. The observed catchability patterns suggest possible high fishing mortality in juvenile Red Grouper related to fishing zone, hook and bait size, and fish length, highlighting the need to consider these variables to improve stock assessments of the Campeche Bank Red Grouper fishery.

Vulnerability of elasmobranchs caught as bycatch in the grouper longline fishery in the Gulf of Gabès, Tunisia

“…On the other hand, the amount of elasmobranchs caught by the demersal longline in the study area is quite high compared to other Mediterranean areas such as the Aegean Sea (Stergiou et al, 2002), the Gökova Bay (Gülşahin & Soykan, 2017), the Adriatic Sea (Ungaro et al, 2005;Carluccio et al, 2021), and Corsica (Bousquet et al, 2022). These differences could be related to several parameters including the environment, species abundance, configuration of the fishing gear, fishing ground, hook size, bait type and soak time (Rincón-Sandoval et al, 2019).…”

“…Furthermore, at least 15 species were caught by demersal longlines off the Lebanese coasts (Lteif, 2015). The differences in species diversity could be related to the species biology (e.g., distribution, reproductive periodicity), the positioning and depth of the species in the water, fishing technique and strategy, the environmental conditions and fishing grounds as well as to dissimilar fishing efforts between areas (Rincón- Sandoval et al, 2019).…”

“…Additionally, C. plumbeus, M. mustelus, and G. cemiculus use the area as primary and secondary nursery grounds (Enajjar et al, 2015). Alternatively, this dominance could be ascribed to the selectivity of the gear, the configuration of the fishing gear and the hook depth (Pennino et al, 2016;Rincón-Sandoval et al, 2019).…”

Length-Based Spawning Potential Ratio (LB-SPR) for Red Grouper (Epinephelus morio) and Associated Species in the Commercial Fishery of the Yucatan Peninsula, Mexico

“…Tis feet predominantly targets juvenile red grouper due to their substantial abundance in the fshing areas along the shallow waters of the Yucatan coastline [13,36,37,72,97]. Te heightened vulnerability of this age group to fshing gear, specifcally the bottom longline, commonly employed in the red grouper fshery by this feet [98], contributes to the increased capture.…”

“…Tese management actions have been exclusively focused on the target species, red grouper (E. morio). However, this management approach has not proven entirely efective in controlling recruitment and growth overfshing, since the impact on juvenile red grouper persists, as indicated by several studies [97,98].…”