Adaptation of diet in a changed environment: Increased consumption of lobster krill Munida gregaria (Fabricius, 1793) by Argentine hake

Abstract

A well‐replicated decadal‐term (2005–2014) stomach content data set was analysed in order to infer inter‐annual fluctuations in the diet of the Argentine hake, Merluccius hubbsi, an opportunistic predator in the San Jorge Gulf (SJG) ecosystem in the Southwest Atlantic. Ten research cruises were carried out each year during January from 2005 to 2014. A total of 18,461 specimens of Me. hubbsi was analysed, of which 6,777 (36.71%) contained food in their stomachs. The diet of Me. hubbsi changed markedly from 2011 onwards, with much greater consumption of the lobster krill Munida gregaria compared to the years before 2011. The frequency of occurrence (%F) of Mu. gregaria in the stomach contents of Argentine hake increased from the year 2009 onwards, most noticeably since 2011, and mostly over the southern region of the SJG. The main predators of Mu. gregaria in the SJG are two species of teleost fish (pink cusk eel, Genypterus blacodes, Argentine seabass, Acanthistius brasilianus) and three Rajidae skates (Zearaja chilensis, Psammobatis spp. and Sympterygia bonapartii), which exhibited decreased catches in the years analysed. The increased consumption of Mu. gregaria by Me. hubbsi, coupled with decreased trends in abundance of the main predators of the lobster krill during the last decade, indicate that top‐down trophic dynamic control occurs in the SJG ecosystem.

Seasonal and spatial variability in condition of age‐0+ Argentine hake Merluccius hubbsi Marini, 1933, in the San Jorge Gulf (Argentina): A bottom‐up perspective

“…gregaria ) in relation to an increase in chl‐ a concentration would favor its prevalence over the benthic morphotype ( M. subrugosa ) (Ravalli, De la Garza, & López Greco, 2013; Varisco, 2013). The preference for euphausiids over other prey items was mentioned in previous studies, which mostly corresponded to summer records (Temperoni et al., 2013 and references therein), as well as the increasing importance of M. gregaria in M. hubbsi diet, particularly since 2011 (Belleggia, Giberto, & Bremec, 2017). The positive selection of both prey by age‐0+ hake, irrespective of the season, could be related with their better nutritional quality in energetic terms over other available prey such as amphipods or other decapods, as observed by Temperoni and Derisio (2018) in spring.…”

“…For the SJG ecosystem, Belleggia et al. (2017) suggested a top‐down trophic dynamic system controlled by predators. While predation may be an important cause of mortality, the measurement of its direct impact in the field is exceptionally difficult and presently no data are available to appropriately test its effect.…”

Network Analysis Can Detect Changes In Food Web Stability Produced By Bottom Trawl Fishery In Patagonia

“…The inclusion of the fishery node and the availability of discard should produce a re-configuration of energy fluxes. Many changes have been reported from the beginning of fishery exploitation, 40 years ago, For example, a decrease in the size of landed hake of the southern stock between 1990 and 2013, 76 a decrease in the abundance of Acanthistius patachonicus, Genypterus blacodes, Zearaja chilensis, Psamobatis spp and Sympterygia spp in the catch of scientific surveys between 2005 and 2014, 77 and the recent increase in abundance of Munida gregaria 67,68 that is also a connected species (a common prey). Thus ,all these changes reflect an important modification of energy fluxes likely produced by the fishery, we were unable to quantify these changes but all the network metrics imply a decrease in stability that in turn suggest the system could change its state, and influence the ecosystem functioning.…”

Who let the young‐of‐the‐year (YOY) up? The pelagic habitat as a nursery and feeding ground area for the YOY Argentine hake Merluccius hubbsi Marini, 1933

“…The Argentine hake exhibited ontogenetic shifts with increased consumption of fish and cephalopods with predator size (Angelescu & Cousseau, 1969; Belleggia et al ., 2014; Sánchez, 2009; Sánchez & García de la Rosa, 1999) and seasonal changes related to prey availability (Belleggia et al ., 2014; Sánchez & Prenski, 1996). Since 2008, and more intensely in 2011, there were changes in the diet of Argentine hake with increased consumption of the lobster krill Munida gregaria (Belleggia et al ., 2017). The species is considered as a facultative opportunist, being able to select high energy density prey species to satisfy their energetic and nutritional requirements, disregarding less caloric content food items even when they are abundant in the environment (Belleggia et al ., 2019).…”

“…The species is considered as a facultative opportunist, being able to select high energy density prey species to satisfy their energetic and nutritional requirements, disregarding less caloric content food items even when they are abundant in the environment (Belleggia et al ., 2019). The frequency of occurrence of cannibalism in the Patagonian stock varied from 3.4% to 12.75% (Belleggia et al ., 2014; Belleggia et al ., 2017; Belleggia et al ., 2019; Ruiz & Fondacaro, 1997; Sánchez, 2009; Sánchez & García de la Rosa, 1999). The Patagonian stock of Argentine hake reproduces in waters off the Chubut province, between 43° and 45° S and from 50 to 100 m depth (Macchi et al ., 2007), during spring and summer through several spawning events with the main peak in January (Macchi et al ., 2004; Macchi et al ., 2018; Pájaro et al ., 2005).…”