Spatio-temporal variability in the cannibalistic behaviour of European hake Merluccius merluccius : the influence of recruit abundance and prey availability

2015 ◽  
Vol 86 (4) ◽  
pp. 1319-1334 ◽  
Author(s):  
I. Preciado ◽  
A. Punzón ◽  
F. Velasco
Author(s):  
J.E. Cartes ◽  
J. Rey ◽  
D. Lloris ◽  
L. Gil de Sola

The feeding intensity and the diet of Merluccius merluccius were studied along a 1000 km latitudinal scale on the coasts of the Iberian Peninsula (western Mediterranean) in spring 2000. Merluccius merluccius was distributed along two bathymetric bands corresponding to the deep continental shelf (between 36 to 148 m), and the upper slope (between 215 to 310 m). At the shelf small crustaceans (mainly euphausiids and mysids) were dominant in the diet while fish (mainly Myctophidae) were the preferred prey on the slope. Feeding intensity of hake was significantly higher in areas with higher hake density suggesting feeding aggregations. Also, feeding intensity was significantly correlated with phytoplankton pigment concentrations (ppc), though only with ppc recorded one month before on the hake sampling stations. This delay between ppc and feeding intensity of hake may be a response to higher prey availability, because most hake prey were pelagic in origin (euphausiids, Clupeiformes) and they may reach high densities after exploiting local phytoplankton blooms. This delayed response seems to have more a local or spotted pattern. During three 8-h sampling cycles food consumed by hake ranged between 1·01 to 5·51% body wet weight (BWW), on average within the range of food consumption rates of other benthopelagic, active swimmer, fish.


2016 ◽  
Vol 179 ◽  
pp. 291-301 ◽  
Author(s):  
Alfonso Pita ◽  
Ana Leal ◽  
Angie Santafé-Muñoz ◽  
Carmen Piñeiro ◽  
Pablo Presa

2021 ◽  
Vol 8 ◽  
Author(s):  
Francisco Izquierdo ◽  
Iosu Paradinas ◽  
Santiago Cerviño ◽  
David Conesa ◽  
Alexandre Alonso-Fernández ◽  
...  

The protection of fish nurseries has been recognized as a useful tool to efficiently manage fisheries given that protected areas enhance the recruitment of target species. To identify and locate potential nursery areas, a solid understanding of species-environment relationships and their spatio-temporal dynamics is needed. Within this context, in this study we assess where European hake (Merluccius merluccius) recruits persistently aggregate in the northern continental shelf of the Iberian Peninsula. Hake recruit data collected during scientific trawl surveys between 2005 and 2016 were analyzed using Bayesian hurdle hierarchical spatio-temporal models, considering the environmental variables bathymetry, sea bottom temperature and salinity. Additionally, three different spatio-temporal structures (i.e., persistent, progressive, or opportunistic) were compared to assess the temporal persistence of nurseries over time. Among all the environmental variables analyzed, bathymetry was the most important. The preferential habitat of recruits was found to be within a bathymetric range of 120–200 m. Our findings clearly show that there is a temporally persistent main nursery located along the continental shelf of the Artabrian gulf (off La Coruña) in addition to several areas with high aggregations of hake recruits but with strong inter-annual variability. We argue that the analytical framework applied in this study allowed us to identify European hake nurseries in the northern continental shelf of the Iberian Peninsula, as well as their spatio-temporal fluctuations throughout the study period (2005–2016), and to assess which environmental factors, among bathymetry, sea bottom temperature and salinity, influence the occurrence and abundance of recruits in the study area. Results of our models also produce a new abundance index that could be useful for improving traditional stock assessment models.


2020 ◽  
Vol 83 (S1) ◽  
pp. 21 ◽  
Author(s):  
Letizia Sion ◽  
Walter Zupa ◽  
Crescenza Calculli ◽  
Germana Garofalo ◽  
Manuel Hidalgo ◽  
...  

The present study provides updated information on the occurrence, abundance and biomass distribution patterns and length frequencies of Merluccius merluccius in the Mediterranean Sea, by analysing a time series of data from the Mediterranean International Trawl Surveys (MEDITS) from 1994 to 2015. The highest values of abundance and biomass were observed in the Sardinian Seas. The use of a generalized additive model, in which standardized biomass indices (kg km–2) were analysed as a function of environmental variables, explained how ecological factors could affect the spatio-temporal distribution of European hake biomass in the basin. High biomass levels predicted by the model were observed especially at 200 m depth and between 14°C and 18°C, highlighting the preference of the species for colder waters. A strong reduction of biomass was observed since the year 2009, probably due to the strengthening of the seasonal thermocline that had greatly reduced the availability of food. The general decrease in biomass of several stocks of anchovy and sardine, preys of European hake, might be indirectly connected to the decreasing biomass detected in the present study. The length analysis shows median values lower than 200 mm total length of most of the investigated areas.


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