Stock assessment for the western winter-spring cohort of neon flying squid (<em>Ommastrephes bartramii</em>) using environmentally dependent surplus production models

Abstract

Summary:The western winter-spring cohort of neon flying squid, Ommastrephes bartramii, is targeted by Chinese squidjigging fisheries in the northwest Pacific from August to November. Because this squid has a short lifespan and is an ecological opportunist, the dynamics of its stock is greatly influenced by the environmental conditions, which need to be considered in its assessment and management. In this study, an environmentally dependent surplus production (EDSP) model was developed to evaluate the stock dynamics of O. bartramii. Temporal variability of favourable spawning habitat with sea surface temperature (SST) of 21-25°C (P s ) was assumed to influence carrying capacity (K), while temporal variability in favourable feeding habitat areas with different SST ranges in different months (P f ) was assumed to influence intrinsic growth rate (r). The parameters K and r in the EDSP model were thus assumed to be linked to temporal variability in the proportion of P s and P f , respectively. According to Deviance Information Criterion values, the estimated EDSP model with P s was considered to be better than the conventional surplus production model or other EDSP models. For this model, the maximum sustainable yield (MSY) varied from 210000 to 262500 t and biomass at MSY level varied from 360000 to 450000 t. The fishing mortality rates of O. bartramii from 2003 to 2013 were much lower than the fishing mortality at target level and MSY level (F tar and F MSY ) and stock biomass was higher than B MSY , suggesting that this squid was not in the status of overfishing and stock was not overfished. The management reference points in the EDSP model for O. bartramii were more conservative than those in the conventional model. This study suggests that the environmental conditions on the spawning grounds should be considered in squid stock assessment and management in the northwest Pacific Ocean.Keywords: Ommartrephes bartramii; stock assessment; surplus production model; environmental factors; Northwest Pacific Ocean.Evaluación de la cohorte occidental de invierno-primavera del calamar volador neon (Ommastrephes bartramii) utilizando modelos de producción excedente dependientes del medio ambiente Resumen: La cohorte occidental de invierno-primavera de los calamares voladores neon, Ommastrephes bartramii, es objeto de las pesquerías chinas de calamares que operan con jigging en el Pacifico Noroeste, desde agosto a noviembre. Debido a que esta especie tiene un ciclo de vida corto y es ecológicamente oportunista, la dinámica de este stock de calamares está muy influenciada por las condiciones ambientales, las cuales necesitan ser consideradas en su evaluación y manejo. En este estudio fue desarrollado un modelo de producción excedente ambientalmente dependiente (PEAD), para evaluar la dinámica del stock de O. bartramii. Se asumió que la variabilidad temporal de un hábitat favorable para el desove sea a una temperatura superficial del mar de 21-25°C (P s ), para influir en la capacidad de carga (K); mientras que la variabilidad...

North Atlantic Oscillation and fisheries management during global climate change

“…In this line, Rykaczewski and Checkley (2008) performed an environmentally dependent surplus production model (EDSP), modifying the Fox surplus production model so that the carrying capacity of the population varies annually as a function of environmental conditions. Other examples of EDSP models have been performed in neon flying squid [Ommastrephes bartramii (Lesueur, 1821)] and Argentine shortfin squid [Illex argentinus (Castellanos, 1960)] with robust predictions (Wang et al 2011(Wang et al 2018.…”

Nonparametric spatiotemporal analysis of violent crime. A case study in the Rio de Janeiro metropolitan area

“…In the northwest Pacific, Wang et al (2016) calculated the abundance of the western winter-spring cohort of O. bartrami by a surplus production model with carrying capacity (K) proportioned to sea-surface temperature in the spawning habitat and growth rate (r) proportional to sea-surface temperature in the feeding habitat. Including the environmental variable of seas-surface temperature was again found to improve model fit, with more conservative management reference points than the conventional surplus production model.…”