The spawning strategy of European hake (Merluccius merluccius, L. 1758) across the Western and Central Mediterranean Sea

Abstract

The oocyte maturation and spawning pattern of European hake Merluccius merluccius, one of the most important species in the Mediterranean fishery, were investigated using data collected in a scientific trawl survey (Mediterranean International Trawl Survey, MEDITS) as well as commercial landing data collected in several geographical sub-areas (GSAs): the Southern and Central Tyrrhenian Sea (GSA10), Sardinia (GSA11), the Southern Adriatic Sea (GSA18) and the Western Ionian Sea (GSA19). The lack of the validation of macroscopic maturity scales is one impediment to obtaining reliable estimates of the reproductive parameters used to assess a fish stock. The MEDITS maturity scale was validated for female European hake by histological analysis of the oocyte diameter frequency distributions and according to the gonadosomatic index. The oocyte diameter frequency distributions and histological analysis confirmed that the ovarian organisation of hake was asynchronous, including a batch spawning pattern and indeterminate fecundity. Females in spawning condition were recorded throughout the year in all GSAs although the main peaks of spawning activity were in winter and in late summer and early autumn. The L 50 estimated for GSA10, GSA11, GSA18, GSA19 were 33.03 cm, 30.03 cm, 31.95 cm and 32.95 cm, respectively. Moreover, no significant trends in the annual estimate of L 50 from 2007 to 2015 in any of the study areas were observed. Mean batch fecundity and relative fecundity (360,687 eggs/fish, 281.6 eggsg −1 in GSA10, 361,311 eggs/fish, and 262.2 eggs g −1 in GSA18) were higher than those reported in other Mediterranean areas.

The poor health of deep‐water species in the context of fishing activity and a warming climate: will populations of Molva species rebuild or collapse?

“…For many demersal species such as gadoids, energy stores mostly comprise lipid stored in their liver, and therefore, the hepato‐somatic index (HSI) is a more accurate measure of their condition than simple morphometric indicators (Lloret et al, 2012). On the contrary, parasitic infection can also be an important health indicator and has been shown to affect natural mortality, growth, fecundity and recruitment in gadoid species, such as European hake ( Merluccius merluccius ) in the Mediterranean (Carbonara et al, 2019; Ferrer‐Maza et al, 2014). Thus, in the case of the northern Catalan coast (Spain, north‐west Mediterranean), data on liver weights and parasitism of M. macrophthalma were obtained to gain further insight into the health status of this population.…”

Investigating the Ovarian Microstructure in the Genera Helicolenus and Scorpaena (Teleostei, Sub-Order Scorpaenoidei) with Implications for Ovarian Dynamics and Spawning

“…This pattern, already found in H. dactylopterus [ 74 , 77 ], has never been observed in the Scorpaena species here analysed, thus, it seems to corroborate the hypothesis of an indeterminate fecundity, clearly distinguishing these species from fish characterized by determinate fecundity, in which very low values of incidence of atresia are expected even at the end of the spawning season (e.g., [ 79 , 80 ]). Usually, fish with indeterminate fecundity, such as Merluccius merluccius [ 47 ], Trachurus trachurus [ 81 ], and Scomber scombrus [ 82 ], show a continuous oocyte recruitment throughout the spawning period exhibiting high fraction of early secondary growth oocytes, such as that observed in our species. Currently, the fecundity type designation of H. dactylopterus is not unanimous: ref.…”

“…The size composition of oocytes was obtained measuring only oocytes where the nucleus was clear, and given that these oocytes are rarely perfectly spherical in shape, in order to reduce the variance, the diameter of each oocyte was taken using TpsDig software [ 44 ], and calculated as average of the major and minor axis [ 45 , 46 , 47 ]. For each species, at the maturing and mature/spawner maturity stages, the thickness of zona pellucida (µm) of oocytes ( n = 35 for each stage) from the cortical alveoli stage to the germinal migration stage was taken.…”

Ichthyoplankton assemblages and physical characteristics of two submarine canyons in the south central Tyrrhenian Sea

“…The high richness and elevated abundance of fish eggs and larvae found in these summer spring and summer spawners (Palomera et al, 2007;Reglero et al, 2012). In contrast, demersal species, such as gadids and flatfish in the central Tyrrhenian Sea, are mostly winter and spring spawners (Carbonara et al, 2019;Recasens et al, 2008). There is anecdotal evidence from local artisanal fishermen of catches of mature Mediterranean hake females during the winter months in the vicinity of these canyons, further corroborating the presence of elevated spawning activities in the region.…”