Study of reproduction of anchovy Engraulis encrasicolus (Actinopterygii, Engraulidae) in the central area of the Moroccan Atlantic coast

Abstract

Morocco is one of the four regions in the world known for the richness of its fish resources in its coasts (through upwelling). The upwelling phenomenon is the origin of high biological productivity of the regions which results in a strong richness of the pelagic resources (sardines, anchovies, mackerel, etc.). These species were defined as fish living in the sea between the surface and 200 meters deep and characterized by significant horizontal and vertical migration in coastal waters [1]. They make up the largest share of global marine catch and they represent quantitatively the main exploited resources, and account for almost 80 % of catches [2,3]. The socioeconomic importance of sea fishing requires managers to strengthen the biological studies necessary for the evaluation of these resources in order to allow fishermen to make the most of natural stands on one hand, and to safeguard stocks by appropriate regulatory measures on the other hand. The anchovies Engraulis encrasicolus Linnaeus, 1758 are an essential element of food chain [4]. Little is known about the biology of this species in the Atlantic waters of Morocco. It is generally admitted the existence of one unique stock for North West Africa, which extends from Morocco to Sierra Leona. Nowadays, the occurrence of different modal classes detected in acoustic surveys carried out in Moroccan and Mauritanian waters raises out the possibility of the existence of different stocks [5]. Most of the research on the ecology of this species was performed in the northern Mediterranean Sea [6][7][8][9], the Black Sea and the Azov Sea [10][11][12], the Adriatic Sea [13,14] or the Bay of Biscay [15][16][17][18]. Despite the significant economic importance of this species along the North African Atlantic coast, little information is known either on its ecology or biology. Populations of small pelagic fish, such as sardine and anchovy, show evidence of important natural fluctuations in their abundance [19,20]. These fluctuations seem to be related, among other factors, to climate variability [21] or habitat conditions [9]. Growth and reproduction are two important parameters in fish population dynamics. Therefore, the present paper is focused on the study of E. encrasicolus reproduction and growth; particularly sex-ratio, gonado-somatic index, condition factor and the size at first maturity were studied. Maarif, B.P. 5366, Casablanca, Morocco. 3 National Fisheries Research Institute, Sidi Abderrahmane Road, Equestrian Club Ould Jmel, B.P. 20050, Casablanca, Morocco Abstract A study on the sexual cycle, of the European anchovy, the pelagic fish, Engraulis encrasicolus (Clupeiformes, Engraulidae), was carried out in the Central Atlantic Moroccan coast in the period between January 2013 and December 2013. This work represents the first attempt to investigate the reproductive features of the E. encrasicolus population in this area. The sex ratio for all fish (1:1.32) was in favour of females. The macroscopic examination of the gonads showed that this specie is matu...

Reproductive biology of the anchovy (Stolephorus commersonnii, Lacepède, 1803) and spotted sardine (Amblygaster sirm, Walbaum, 1792) from Tanga Region, Tanzania

“…This signifies that fishes that belong to the same species may attain first maturity at different sizes depending on the condition of the environments they inhabit and other associated factors. This is in agreement with other scientists who suggested that the growth of fish could be retarded by environmental conditions and food resources (Wootton, 1990) and pressure exerted from fishing activities (Baali et al, 2017).…”

“…Moreover, changes in size at first maturity may be ascribed to the different strategies utilised by fish in different environments to better adapt to environmental conditions (Baali et al, 2017). This study also demonstrated that males of both species attained first sexual maturity at smaller sizes than females.…”

“…commersonii and A. sirm revealed a skewed size-dependent sex ratio with females dominating in larger size classes during this study. This was also evident in other tropical and sub-tropical waters for Stolephorus hetrolobus (Milton et al, 1990), and anchovies like Engraulis encrasicolus (Baali et al, 2017) and A. sirm (Veerappan et al, 1997). This could be ascribed to a number of factors including faster growth of females resulting in them becoming vulnerable to fishing gear, and displaying different migratory movements as compared to males (Abderrazik et al, 2016), and natural mortality differing between the sexes (Turner et al, 1983).…”

Antxoaren maneiu eta kontserbazioa: biomasan eragiten duten faktoreen azterketa

“…Antxoaren populazio-dinamika nagusiki errekrutamenduaren mendekoa da, hots, ale helduen multzoari urtero gehitzen zaizkion ale berrien ko-Antxoaren maneiu eta kontserbazioa: biomasan eragiten duten faktoreen azterketa puruaren mendekoa [6]. Antxoak errundako arrautza kopuruaren eta bertatik jaiotako larben kopuruaren eta helduen kopuruaren artean erlazio zuzenik ez egoteak agerian uzten du inguruneak (eragile biotiko eta abiotikoak) fase goiztiarreko heriotza-tasan eragin zuzena duela [7]. Era berean, Aldanondok [8] jakinarazi zuen urteko errekrutamenduan eragin handia izan zezaketen eragileetako bi erreklutamenduari berari loturiko hilkortasuna (arrautzen eta larba goiztiarrena) eta baita aleen neguko hilkortasuna izan zitezkeela.…”

“…Edozein animalia helduren egoera biologikoan, erreserba energetikoek berebiziko garrantzia dute. Zenbat eta erreserba energetiko gehiago izan animaliak, orduan eta egoera biologiko hobea izango du; izan ere, erreserba energetiko nahikoa ez izateak baldintza kaskarreko egoerei aurre egiteko aukerak murrizten ditu [9]. Hots, indibiduo batek oinarrizko funtzioak betetzeko adina energia badu soilik, oinarrizko funtzio horiek aldatzen dituen edozein ingurune-baldintzak indibiduo horren heriotza ekar lezake.…”