Mediciones in situ de fuerza de blanco de anchoveta (engraulis ringens) a partir de datos colectados con una ecosonda comercial durante operaciones de pesca industriales en el stock norte-centro peruano.
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Date
2025
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Universidad de Concepción
Abstract
Los pequeños pelágicos que habitan los Ecosistemas de Afloramiento de Borde Este (EBUS) como la anchoveta peruana (Engraulis ringens) se caracterizan por su importancia económica (sustentan grandes pesquerías), ecológica (son componentes centrales de las redes tróficas) y por la alta variabilidad espacio-temporal de su biomasa. Debido a esta variabilidad (cada vez más alta producto del cambio climático) y para lograr un mejor manejo adaptativo es necesario que los stocks de anchoveta sean monitoreados con la mayor frecuencia posible. En ese sentido, la información colectada por las embarcaciones comerciales durante las temporadas de pesca -periodos en los que la anchoveta no es evaluada mediante cruceros sistemáticos- podría ser utilizada para generar indicadores que ayuden alcanzar dicho objetivo. En este trabajo se estimó la fuerza de blanco de anchoveta (target strength, TS, parámetro fundamental para la estimación de biomasa) dentro del área correspondiente al stock Norte-Centro peruano (NC, 3°30’S-16°00’S) y se estudió el efecto de la talla (L), profundidad, fases del día, ángulos de inclinación y distancia al centro del eje acústico sobre dicha variable. Asimismo, se investigó los comportamientos de natación individual y patrones de orientación grupal de dicha especie. También se comparó los TS y velocidades de natación de E. ringens con lo publicado para el género Engraulis. Se utilizó datos acústicos colectados por una ecosonda comercial ES60 instalada en una embarcación cerquera durante sus faenas de pesca en el stock NC entre mayo y julio de 2017. Durante el periodo analizado, la anchoveta presentó TS de individuos grandes (L≥13.5 cm) mucho más altos respecto a los valores actualmente utilizados en las evaluaciones oficiales de anchoveta en Perú. También se encontró que el TS de anchoveta estuvo fuertemente influenciado por la profundidad y que los TS estimados durante la noche fueron más altos que los del día. En cuanto a las otras variables explicativas, solamente los ángulos de inclinación vertical y la distancia al centro del eje acústico tuvieron influencia sobre el TS. Se encontró tres tipos de comportamientos de natación individuales: Ondulatorio (predominante), Directo y Estacionario (casi inexistente). Los patrones grupales de orientación verticales fueron mucho más fuertes y homogéneos que los horizontales. A nivel interespecífico, E. ringens presentó los TS más bajos del género Engraulis. A nivel intraespecífico, se observó que los TS de E. ringens estimados en la zona del stock NC peruano fueron mucho más bajos que aquéllos provenientes de las tres Unidades Demográficas chilenas. Finalmente, las velocidades de natación individuales de la anchoveta en el Mar Peruano fueron ~50% más bajas que aquéllas estimadas en el Mar Chileno.
Small pelagic fish that inhabit Eastern Boundary Upwelling Systems (EBUS) such as Peruvian anchovy (Engraulis ringens) are characterized by their economic (they sustain big fisheries) and ecological (they are key components of trophic webs) importance and for the high variability of their biomass. Due to such variability (constantly increasing as consequence of climate change) and, to improve their adaptative management, anchovy stocks should be monitored as frequently as possible. In that sense, information collected by commercial vessels during fishing seasons -periods in which anchovy is not assessed through systematic surveys- could be used to generate proxies that help to reach this goal. In this work, we computed the target strength of anchovy (TS, crucial for biomass estimations) inside the area corresponding to the Peruvian North-Center stock (NC, 3°30’S-16°00’S). Influence of body length (L), depth, phases of the day, orientation angles and distance from acoustic axis on TS were explored. Individual swimming behaviors and group orientation patterns were also investigated. We also compared TS and individual swimming speeds of E. ringens with that published for the Engraulis genus. We used acoustic data collected by a commercial echosounder ES60 installed in a purse-seiner during its fishing operations throughout NC stock between May and July 2017. For the studied period, anchovy exhibited highest TS values for big individuals (L≥13.5 cm) compared with those currently used in official biomass estimations in Perú. We also found that anchovy TS was strongly influenced by depth and that TS estimated at night were higher than those computed at day. About the other explanatory variables, only tilt angles and distance to the center of the acoustic axis had influence on TS. We found three types of individual swimming behaviors: Undulatory (predominant), Direct and Stationary (almost inexistent). Vertical group orientation patterns were more homogeneous and stronger than horizontal ones. At interspecific level, E. ringens exhibited the lowest TS values of the Engraulis genus. At intraspecific level, we observed that TS of E. ringens from Peruvian NC stock were lower than those from the three Chilean Demographic Units. Lastly, individual swimming speeds of anchovy computed from Peruvian Sea were ~50% slower than those estimated from Chilean Sea.
Small pelagic fish that inhabit Eastern Boundary Upwelling Systems (EBUS) such as Peruvian anchovy (Engraulis ringens) are characterized by their economic (they sustain big fisheries) and ecological (they are key components of trophic webs) importance and for the high variability of their biomass. Due to such variability (constantly increasing as consequence of climate change) and, to improve their adaptative management, anchovy stocks should be monitored as frequently as possible. In that sense, information collected by commercial vessels during fishing seasons -periods in which anchovy is not assessed through systematic surveys- could be used to generate proxies that help to reach this goal. In this work, we computed the target strength of anchovy (TS, crucial for biomass estimations) inside the area corresponding to the Peruvian North-Center stock (NC, 3°30’S-16°00’S). Influence of body length (L), depth, phases of the day, orientation angles and distance from acoustic axis on TS were explored. Individual swimming behaviors and group orientation patterns were also investigated. We also compared TS and individual swimming speeds of E. ringens with that published for the Engraulis genus. We used acoustic data collected by a commercial echosounder ES60 installed in a purse-seiner during its fishing operations throughout NC stock between May and July 2017. For the studied period, anchovy exhibited highest TS values for big individuals (L≥13.5 cm) compared with those currently used in official biomass estimations in Perú. We also found that anchovy TS was strongly influenced by depth and that TS estimated at night were higher than those computed at day. About the other explanatory variables, only tilt angles and distance to the center of the acoustic axis had influence on TS. We found three types of individual swimming behaviors: Undulatory (predominant), Direct and Stationary (almost inexistent). Vertical group orientation patterns were more homogeneous and stronger than horizontal ones. At interspecific level, E. ringens exhibited the lowest TS values of the Engraulis genus. At intraspecific level, we observed that TS of E. ringens from Peruvian NC stock were lower than those from the three Chilean Demographic Units. Lastly, individual swimming speeds of anchovy computed from Peruvian Sea were ~50% slower than those estimated from Chilean Sea.
Description
Tesis presentada para optar al grado de Magíster en Ciencias con Mención en Pesquerías.
Keywords
Pesca, Anchoveta peruana