Estimating the impact of COVID-19 pandemic on alternative semi-intensive shrimp (Penaeus vannamei) production schedules in Mexico: a stochastic bioeconomic approach.

This study uses a stochastic bioeconomic approach to estimate the COVID-19 pandemic economic impact on shrimp farming in Mexico. Seeding-harvesting schedules - March-June, May-August, and August-November - were analyzed using shrimp prices and production costs corresponding to 2017-2019 (pre-pandemic) and 2020 (pandemic). The analyses estimated net revenue varied within 597.97-2758.88 USD$ ha-1 and 1262.40-1701.32 USD$ ha-1 under the pre-pandemic and pandemic scenarios, respectively. Significant decreases (38%) were estimated in net revenue values in March-June and May-August under the pandemic scenario. However, probability distributions estimated that uncertainty on the expected net revenues was not affected by the pandemic conditions, and the probability of losing was null or negligible in all the cases. Unfavorable conditions under the pandemic also required significantly higher break-even production for March-June (25.7%) and May-August (28.5%) schedules. The cost of post-larvae was the most important economic factor influencing net revenue. To conclude, although the operating conditions during the pandemic were conducive to worsening the economic outcome, no evidence still exists that uncertainty and economic risk increased compared with pre-pandemic conditions.

Inter-cohort growth for three tropical resources: tilapia, octopus and lobster.

Growth parameters are an important component for the stock assessment of exploited aquatic species. However, it is often difficult to apply direct methods to estimate growth and to analyse the differences between males and females, particularly in tropical areas. The objective of this study was to analyse the inter-cohort growth of three tropical resources and discuss the possible fisheries management implications. A simple method was used to compare individual growth curves obtained from length frequency distribution analysis, illustrated by case studies of three tropical species from different aquatic environments: tilapia (Oreochromis aureus), red octopus (Octopus maya) and the Caribbean spiny lobster (Panulirus argus). The analysis undertaken compared the size distribution of males and females of a given cohort through modal progression analysis. The technique used proved to be useful for highlighting the differences in growth between females and males of a specific cohort. The potential effect of extrinsic and intrinsic factors on the organism's development as reflected in the size distribution of the cohorts is discussed.

Inter-cohort growth for three tropical resources: tilapia, octopus and lobster / Crecimiento ínter-cohorte para tres recursos tropicales: tilapia, pulpo y langosta

Growth parameters are an important component for the stock assessment of exploited aquatic species. However, it is often difficult to apply direct methods to estimate growth and to analyse the differences between males and females, particularly in tropical areas. The objective of this study was to analyse the inter-cohort growth of three tropical resources and discuss the possible fisheries management implications. A simple method was used to compare individual growth curves obtained from length frequency distribution analysis, illustrated by case studies of three tropical species from different aquatic environments: tilapia (Oreochromis aureus),red octopus (Octopus maya)and the Caribbean spiny lobster (Panulirus argus).The analysis undertaken compared the size distribution of males and females of a given cohort through modal progression analysis. The technique used proved to be useful for highlighting the differences in growth between females and males of a specific cohort. The potential effect of extrinsic and intrinsic factors on the organism's development as reflected in the size distribution of the cohorts is discussed.

Los parámetros de crecimiento son un componente importante para la evaluación de las poblaciones de especies acuáticas explotadas. Sin embargo, es complicado aplicar métodos directos para estimar el crecimiento y analizar las diferencias entre machos y hembras particularmente en zonas tropicales. El objetivo de este estudio fue analizar el crecimiento entre cohortes de tres recursos tropicales y discutir las posibles implicaciones en el manejo pesquero. Se utilizó un método simple para comparar las curvas de crecimiento individual obtenidas a través del análisis de distribución de frecuencias de longitudes, para ello se usaron tres casos de estudio de especies tropicales provenientes de diferentes ambientes acuáticos: tilapia (Oreochromis aureus),pulpo rojo (Octopus maya)y la langosta del caribe (Panulirus argus).El análisis consistió en comparar la distribución de longitudes de hembras y machos obtenidas del análisis de progresión modal. Esta técnica puede ser utilizada para resaltar las diferencias en el crecimiento entre hembras y machos de una cohorte específica. En este documento se discute el efecto potencial de los factores intrínsecos y extrínsecos en el desarrollo de los organismos como se refleja en la distribución de tallas de las cohortes.