Somatic Condition, Growth and Reproduction of Hake, <i>Merluccius merluccius</i> L., in the Portuguese Coast

Abstract

Weight/length relationships, condition factor, gonadosomatic and hepatosomatic indices, conversion factor for gutted to total weight and spawning season of hake in the Portuguese Coast (36.92 to 42.22 degrees latitude N; 9.61 to 6.07 degrees longitude W) were investigated for the first time, aiming to fill the lack of information on the biology of hake of the Portuguese waters. Data were obtained from commercial samples collected between 2005 and 2010 and pooled by month. Sex ratio observed in fish below 40 cm was close to 1:1; females were always dominant above 50 cm length. All the parameters were analysed by month and by sex and by combined sexes. The relationships obtained for combined sexes for the entire period concerning the growth in length and weight were: total length-total weight = 0.0038L 3.172 , total length-gutted weight = 0.0052L 3.059 . The relationship total weight-gutted weight was W t = 15.8112 + 0.8480W g and the conversion factor was of 1.1524. The growth rate is similar for both sexes but different when based on total weight or gutted weight. The analysis of the condition factor, gonadosomatic index, hepatosomatic index and the monthly distribution of the maturity stages seem to indicate that hake from the Portuguese Coast has a long spawning season, with three spawning peaks in March, May and August but the start of the spawning season seems independent of the fish length.

Comparison of some biological aspects between the two sexes of the European hake Merluccius merluccius from the Egyptian Mediterranean waters

“…It is obvious from Table 6 that, M. merluccius in the present study in the Egyptian Mediterranean waters shows no significant differences with Abd El Aziz (1976) and Soliman (1992) in the same region, while this species in the present study was less heavier than those reported in Bay of Biscay (Ices, 1991;Lucio et al, 2000), Iberian Atlantic (Pineiro and Sainza, 2003), Moroccan (Belcaid and Ahmed, 2011), and in Portuguese coast (Costa, 2013). These variations in different regions (Table 6) can be attributed to different conditions of food and temperature prevailing in these areas (Bruton, 1990) and water temperature can also affect fish growth directly by affecting the physiology of the fish (Weatherly and Gills, 1987).…”

Temporal and spatial patterns of reproductive indices of European hake ( Merluccius merluccius ) in the northern North Sea and Norwegian coastal areas

“…Likewise, temporal variation in growth (Domínguez-Petit et al, 2008), skipped spawning and changes in the proportion of immature/mature fish resulting from varying migration intensities, could influence the observed L 50 . The presence of very large hake, some over 100 cm in length, may also explain the high GSI values recorded in July, since larger fish tend to have disproportionally heavier gonads than smaller individuals (Lucio et al, 1998;Costa, 2013). Reproductive indices show that spawning activity is likely to be concentrated during those months with a higher presence of large and mature individuals.…”

“…There is usually good correspondence between macroscopic maturity staging and GSI Costa, 2013), although the coarse resolution of the maturity stages can result in a wide range of GSI values. Hake are serial spawners, and females can release up to 10 batches of eggs (ova) at approximately 5-10 day intervals over a period of several months in the Bay of Bis- Table 2 Size of maturation (L50; length at which 50% of the population reaches maturity) for males and females of European hake in its different areas of distribution.…”

“…Spawning biology of European hake has been extensively studied in other areas of its distribution, such as the Mediterranean (Olivar et al, 2003;Al-Absawy, 2010;Ferrer-Maza et al, 2014), around the Iberian Peninsula (Pérez and Pereiro, 1981;Piñeiro and Saínza, 2003;Costa, 2013), the Bay of Biscay (Martin, 1991;Alvarez et al, 2004; and in the Celtic Sea (Hickling, 1930;Alvarez et al, 2004). Similar information for the North Sea is limited to investigations from the early 20th century (Schmidt, 1909), although monitoring of the biomass and distribution is included in ICES data collection programmes and more recently in annual Norwegian research surveys.…”

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“…Hence, large variations in proximate composition of fish species reflects physiological processes and changes in environmental conditions that together dictate spawning, migration, and starvation or heavy feeding activities (Boran & Karaçam, 2011;Costa, 2013).…”