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.

ABSTRACT. Conspicuous sedimentary deposits forming well-structured and prominent submarine dunes are found on the coast of Yucatan (Mexico), close to the ports of Dzilam de Bravo, San Felipe, and El Cuyo. The objective of this study was to evaluate the morphological and sedimentological features of these submarine dunes. Sub-bottom seismologic profiles were obtained and standardized sedimentological analyses were performed on sediment samples collected at the three study sites. Both the height and wavelength of dunes were different between the three sites, mean heights ranging from 0.84 to 2.28 m and mean wavelengths from 98 to 330 m. Most of the dunes showed a wellmarked asymmetry, which is related to the direction of their movements. Their granulometric composition was dominated by medium, moderately well-sorted sand. This study provides bases for future systematic monitoring of these peculiar ecosystems, including information to be considered for the evaluation of their ecological role in the marine system.Key words: dune field, dune morphology, sub-bottom profiles, sedimentology. RESUMEN.En la costa del estado de Yucatán existen áreas con campos conspicuos de depósitos sedimentarios que forman dunas submarinas bien estructuradas y sobresalientes, aledaños a los puertos de Dzilam de Bravo, San Felipe y El Cuyo. El objetivo de este trabajo fue evaluar la morfología y las características sedimentológicas de estas dunas sumergidas. Para esto, se obtuvieron perfiles sismológicos del subfondo y se realizaron análisis sedimentológicos estandarizados de muestras recolectadas en los tres sitios de estudio. Tanto la altura de las dunas como su longitud de onda fueron diferentes entre los tres sitios, donde se registraron dunas de entre 0.84 y 2.28 m de altura y con longitudes de onda promedio entre 98 y 330 m. La mayoría de las dunas mostró una asimetría bien marcada, que está relacionada con el sentido en que se mueven. En su composición granulométrica dominó el sedimento superficial del tipo arena media moderadamente bien clasificada. Este trabajo sienta bases para el monitoreo sistemático de estos ecosistemas peculiares, incluyendo información para considerarse en la evaluación del papel ecológico que desempeñan en el sistema.Palabras clave: campos de dunas, morfología de dunas, perfiles del subfondo, sedimentología.

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