Aspects of Reproductive Biology of the European Hake (Merluccius merluccius) in the Northern and Central Adriatic Sea (GSA 17-Central Mediterranean Sea)

Abstract

The study focused on the macroscopic, histological, and biometric analysis of European hake females in GSA 17 (Central-North Adriatic Sea). From 2013 to 2015, 976 females were collected and analyzed monthly. Though females in spawning conditions were found during the whole year, the trend of GSI showed a peak of the reproductive season from April to July in 2014 and 2015. HSI and Kn reached the highest values in September, after the spawning peaks. In 2013, the trend of these indices did not highlight an evident peak, probably due to an adverse event that occurred in the previous winter in the Adriatic shelf. The length at first maturity (L50) was estimated by macroscopic and histological approaches, resulting in 30.81 cm for the macroscopical length and 33.73 cm for the histological length; both values are higher than the current catching legal size. For the first time in this area, batch and relative fecundity were estimated. Relative fecundity was similar to the Mediterranean and the Atlantic stocks, whereas batch fecundity values were lower compared to other fishing grounds. Overall, the analysis of reproductive parameters plays a fundamental role in the sustainable management of this resource in an area as overfished as the Central-North Adriatic Sea.

Reproductive Biology of Male European Hake (Merluccius merluccius) in Central Mediterranean Sea: An Overview from Macroscopic to Molecular Investigation

“…The absence of differentiated females in the smallest class (13–14 cm) may be due to a different development between sexes; females mature when they reach a bigger size compared to males [ 20 , 21 ], and in such small sizes specimens could present a still undifferentiated gonad that could convert in the ovary later.…”

“…Several studies on the reproductive biology of European hake have been conducted in different areas [ 10 , 17 , 18 , 19 , 20 , 21 ], but generally on females, which define the spawning stock biomass (SSB).…”

Every animal matters! Evaluating the selectivity of a Mediterranean bottom trawl fishery from a species community perspective

“…Both the legal codends currently in use in the Mediterranean (SM40 and DM50) are known to be insufficiently size selective for many commercial species targeted by bottom trawl fisheries, since individuals below the MCRS and/or the length of first maturity are often retained in the catches [ 1 ]. Regarding the European hake, one of the most landed and overexploited demersal species in the whole region [ 48 ], the two codends were unable to avoid the catch of individuals either below the length of first maturity (more than 30 cm; [ 49 , 50 ]) or below the MCRS of 20 cm. This is in line with several selectivity studies conducted on SM40 and DM50, where the predicted 50% retention length (L50) was always lower than 20 cm in different areas (Adriatic Sea [ 21 , 51 , 52 ]; Aegean Sea [ 53 – 56 ]; Alboran Sea [ 57 ]; Balearic Islands [ 58 , 59 ] Tyrrhenian Sea [ 60 ]).…”

Seasonal Trophic Ecology and Diet Shift in the Common Sole Solea solea in the Central Adriatic Sea

“…The gonadosomatic index (%GSI) is often considered a suitable index to evaluate the temporal variation of maturity stages of gonads in order to define the reproductive cycle [ 47 , 48 ] as a surrogate for reproductive effort, and it was calculated both for all the specimens and for female and male specimens separately as: %GSI = 100 × (gonad weight/body weight). The hepatosomatic index (%HSI), calculated as %HSI = 100 × (liver weight/body weight), was determined as a proxy of metabolic activity [ 33 ].…”