Álvaro Hernández-Flores

The red grouper stock in the Campeche Bank (cb) has been the subject of several assessments of its population status since the 1970s when it was classified as underexploited. Gradually, the condition of the resource began to show signs of overexploitation and in 2000 it was officially declared to be in decline. The present assessment considers the longest series of commercial catches and indices of relative abundance available so far from the two most important Mexican fleets operating in the cb. The Monte Carlo (cmsy) and Bayesian (bms) methods, based on the Schaefer production model, were applied for the stock assessment. The current condition of the red grouper stock was complemented with the analysis of the size structure accessed by the Mexican fleets. The indicators used in this study confirm that in 2019 the red grouper stock in the cb continues to be overexploited with both recruitment and growth overfishing problems. According to the reconstructed stock trajectory, exploitation was emphasized starting in the 1990s, causing a substantial drop in catches with high levels of fishing exploitation, which began to reduce the biomass levels of the population. The biomass level in the last year of the series was estimated to be below 50% of the BMSY, a level at which recruitment may be affected and which may be aggravated by the high proportion of mega-spawners caught by the major fleet. On the other hand, it is shown that the small fleet captures a high percentage of red grouper juveniles, which promotes growth overfishing, so that fishery management strategies for the recovery of the resource should focus on reducing fishing pressure on juveniles that have not reached sexual maturity. Other complementary management measures for the recovery of the resource are also analyzed. Keywords: Red grouper, Epinephelus morio, Yucatán-México, stock assessment.

This chapter briefly describes relevant historical facts of the multispecific red grouper fishery and gives a short biological description of Epinephelus morio and associated species to the fishery. Also, the fleets that target these species are described. During the growth stage the fishery reached the maximum production in the 1970’s, after that the fishery showed a stabilization stage and later a decline stage in the year 2000. During the 1970’s, the Mexican semi-industrial fleet and the Cuban fleet obtained the highest catches. Subsequently, the participation of the Cuban fleet decreased while the Mexican artisanal fleet increased significantly. In 2000, the fishery was officially declared overexploited. After 24 years of efforts, the management measures have not been effective enough to rebuild the stock. In addition, recreational fishing has increased in recent years and is enhancing the state of overexploitation of the resource. This document aims to establish a historical context of the red grouper fishery in Yucatan as a preamble to have a better understanding of its current situation, with a view to proposing in the next chapters a comprehensive management strategy for its recovery in the medium and long term. Keywords: Red grouper, fisheries development, fisheries fleets, rebuilding stock

This introductory chapter contextualizes the origin of this book, as well as the launching of a Network of Yucatan Grouper Researchers dedicated to contribute with their experience and knowledge of the different disciplines and management processes. The relevant thematic content of the chapters in this book is broken down to understand the context of resource deterioration and the biological, ecological, social, economic and management impacts associated with the grouper fishery. The structure of the book and the rationale of the different chapters are summarized and some lessons learned in the integration of information and knowledge are presented, as well as windows of opportunity to improve fisheries governance and reduce uncertainty in assessment, monitoring and management processes. Keywords: Grouper and associated species, fisheries management, transdisciplinary, sustainable fisheries.

Mexican octopus fisheries play an important role in both domestic and international seafood markets, yet little is known about the determinants of retail price in the national frozen octopus sector. This study examines how trade flows and domestic demand interact to shape price dynamics, providing insights into sustainability challenges. Multiple linear regression was employed to test the influence of economic, production, and trade variables on retail prices, based on annual data from 2010 to 2024. The best-performing model identified average daily salary, apparent consumption and import value as significant determinants, explaining more than 90% of the observed variation. Results show that rising salaries and greater domestic consumption are exerting upward pressure on prices, while imports, although limited, contribute to price moderation. Export values have declined, signaling a weakening role of the international markets. These findings suggest that domestic demand is becoming increasingly important for sustaining value in the sector, but this shift could intensify fishing pressure on wild stocks. Strengthening compliance with management measures and aligning policies with domestic market realities are crucial to ensuring long-term sustainability of the Mexican octopus supply.

Nonlinear regression modeling was used to study the nursery production of the oyster Crassostrea virginica in the Celestún (CL) and Rio Lagartos (RL) lagoons in Yucatán, Mexico. Relationships between production parameters and environmental variables were also established. Spat (2.40 ± 0.20 mm) was obtained from a hatchery and reared in Nestier-​type trays using an off-bottom system. Oyster cultivation took place from May 2021 to September 2021 and ended after 122–126 days when oysters reached 30.00 mm. There were no significant differences in final height (CL: 30.80 ± 0.42 mm; RL: 31.80 ± 0.65 mm; P = 0.18) and growth rate (CL: 0.23 ± 0.02 mm·d–1; RL: 0.23 ± 0.01 mm·d–1; P = 0.98). Final survival was 71.45% in CL and 99.40% in RL. Nonlinear regression curves were statistically satisfactory for analyzing growth and survival. Except for dissolved oxygen, mean salinity (CL: 15.23 ppt; RL: 35.02 ppt), temperature (CL: 29.64 °C; RL: 31.02 °C), dissolved oxygen (CL: 4.50 mg·L–1; RL: 5.04 mg·L–1), pH (CL: 8.10; RL: 8.34), chlorophyll a (Chl a) (CL: 3.23 mg·m–3; RL: 6.85 mg·m–3), and total dissolved solids (CL: 16,101 mg·L–1; RL: 34,838 mg·L–1) were significantly higher in RL (P < 0.05). Except for Chl a, the environmental variables were more stable in RL than in CL (P < 0.05). In RL, the growth rate was positively related to salinity and pH. In CL, the growth rate slowed when salinity decreased, and the mortality rate diminished when salinity, dissolved oxygen, and total dissolved solids increased and pH decreased. Salinity was mainly responsible for the observed differences in production between lagoons. Even when temperature and salinity were high in RL, acceptable growth rate and survival were observed, possibly due to stable rearing conditions.

A stochastic model was developed to analyze Crassostrea virginica production when cultivated at three stocking densities, defined as the area occupation (50, 75, and 100%) in Nestier-type trays, using juvenile oysters with an initial size (height) of 29.40 ± 0.18 mm. A 25-week grow-out was first conducted in the Rio Lagartos lagoon, showing that final oyster size was inversely related to density (P < 0.05), ranging from 61.87 mm (100% density) to 68.00 mm (50% density). At the same time, mortality was negligible (lower than 1.0%). The environmental conditions in the lagoon were stable, and the oyster growth rate positively correlated with water temperature and pH. Low pH was associated with slow oyster growth, possibly as an adverse effect of acidic conditions on the oyster shell formation. The model indicated that, for an initial 100,000 oyster population, the maximum production (oyster dozens) is obtained after 20 weeks (8310 at 50% density) and 25 weeks (8250 at 75%, and 6670 at 100% density). There was a 100% probability of oysters reaching a minimum commercial size (MCS) of 60.00 mm when using the 50 and 75% densities and 80.6% when using 100%. The model estimated that, for the maximum density, extending the grow-out up to 32 weeks would allow reaching MCS with 100% probability, although this should be experimentally confirmed. The random variability of oyster production in 50 and 75% densities was minimal, while at 100% density, it was extremely high. A sensitivity analysis indicated that for 50 and 75% densities, the main stochastic elements influencing production, are related to oyster mortality, while at 100% density, they are related to oyster growth.

Comprender la dinámica poblacional de las especies marinas sedentarias en baja densidad es esencial para su manejo sostenible. Cuando estos stocks se exponen a altos niveles de explotación pesquera, el efecto Allee se puede magnificar, provocando fallas en el reclutamiento, colapso del stock y el fracaso de los programas de mejora y restauración, incluso después de que la pesca haya cesado. En este estudio se modeló la depensación a bajas densidades (efecto Allee) en una especie sedentaria bajo el efecto Allee potenciado por la pesca mediante un modelo bioeconómico. Se corrió el modelo bajo el esquema de manejo de acceso abierto para contrastar las implicaciones a largo plazo bajo dos escenarios: efecto Allee “natural” y efecto Allee potenciado por la pesca. Bajo el efecto Allee potenciado, el stock desovante requirió 70% de mayor densidad para mantener una probabilidad de reproducción de 50% o más, comparado con el efecto Allee no potenciado. La simulación mostró que la biomasa total colapsa cinco años antes en el escenario potenciado, con un rendimiento menor en los principales indicadores bioeconómicos. También se identificó un “punto de no retorno” para el stock como resultado del efecto Allee, más allá del cual el stock no se recobraría aun en ausencia de pesca. El manejo debe enfocarse en mantener un stock desovante por arriba del punto de referencia umbral Allee y mejorar la comprensión de la interacción entre el efecto Allee y el esfuerzo de pesca, especialmente para stocks que ya se encuentran en bajos niveles.

Context: Density-dependent marine sedentary species exhibit heterogeneous distribution in response to biological needs and exploitation. Sustainable management requires consideration of factors influencing this distribution, including Allee effects and source–sink dynamics. Aim: This study investigates the implications of the Allee effect and source–sink dynamics in the management of a sedentary species, queen conch (Aliger gigas) on the Pedro Bank Jamaica. Method: We used spatial analysis of spatio-temporal survey data obtained over an 11-year period to determine spatial distribution and preferences. A depensation model along with knowledge of the connectivity of the population was used to model the Allee effect and define source and sink areas. Key results: We found that mate-finding Allee effects and exploitation are major drivers of source–sink dynamics in this population. Sources (the effective spawning stock) consisted of less than 30% of total adult population and were being driven to a low-density stable state because of intensification of the Allee effect from high exploitation. Conclusions: Management must explicitly consider Allee effects and source–sink dynamics to avoid overestimations of stock productivity and spatial mismatches of biological and management units. Stocks should be managed well above determined critical-density thresholds because stocks are unlikely to recover once they fall below them.

The estimation of reliable indices of abundance for sedentary stocks requires the incorporation of the underlying spatial population structure, including issues arising from the sampling design and zero inflation. We applied seven spatial interpolation techniques [ordinary kriging (OK), kriging with external drift (KED), a negative binomial generalized additive model (NBGAM), NBGAM plus OK (NBGAM+OK), a general additive mixed model (GAMM), GAMM plus OK (GAMM+OK) and a zero-inflated negative binomial model (ZINB) ] to three survey datasets to estimate biomass for the gastropod Aliger gigas on the Pedro Bank Jamaica. The models were evaluated using 10-fold cross-validation diagnostics criteria for choosing the best model. We also compared the best model estimations against two common design methods to assess the consequences of ignoring the spatial structure of the species distribution. GAMM and ZINB were overall the best models but were strongly affected by the sampling design, sample size, the coefficient of variation of the sample and the quality of the available covariates used to model the distribution (geographic location, depth and habitat). More reliable abundance indices can help to improve stock assessments and the development of spatial management using an ecosystem approach.