Nematode parasites in the striped mullet (Mugil cephalus Linnaeus, 1758) in the southern Gulf of California

Coastal lagoons are an important component of the Gulf of California as they are considered natural ecosystems with high productivity and home to species of regional economic interest such as the striped mullet (Mugil cephalus), which, for its eating habits tends to present parasitism. The objective of the present work was to identify and determine the number of nematode parasites in the striped mullet in three lagoon systems (Navachiste, La Reforma, and Ceuta) in coastal areas of the southern Gulf of California. Thirty Mugil cephalus were randomly obtained from each of the lagoon systems. From each fish was obtained the total length, weight and condition factor (FC), next was dissected to be analyzed hepatosomatic index (HSI) and determine by direct count the prevalence, average intensity and average abundance of nematode; nematodes are identified taxonomically and molecularly. The nematode parasites found to belong to the genus Contracaecum of the family Anisakidae in all the fish sampled the parasitic prevalence was 67%. The nematode parasites found by sex indicated that 77% of the striped mullet females analyzed were parasitized, while the males presented 59%. The CF obtained was 1.17- 4.07, and the HSI ranged between 0.85 and 1.45; the average intensity for nematodes was 7.45, and the average abundance was 4.97, demonstrating that Contracaecum multipapillatum is the main nematode parasite present in all lagoon systems the southern Gulf of California.

Life-history traits of the striped red mullet Mullus surmuletus (Linnaeus, 1758) in the south Aegean Sea (eastern Mediterranean)

Although the red striped mullet is one of the main target fish of the Hellenic demersal fisheries, information about its biology is limited. The aim of this study was to describe the reproductive biology and growth of the species in the south Aegean Sea based on 1032 individuals sampled under the Data Collection Framework Program in 2016. According to the monthly variation of the maturity stages and the gonadosomatic index, spawning activity took place from March to July, although it appeared to occur throughout the year. Length at 50% maturity (L50) was 153.3 and 139.2 mm in females and males, respectively. Individual ages were determined by counting the annuli of otoliths macroscopically. Marginal increment analysis (MIA) combined with complementary information derived from otolith edge analysis, the assessment of the reproductive period and the length–frequency distribution modes of the population showed that annulus formation occurs between February and April. The length–weight relationship revealed a significant sex effect and was described by the parameters α = 0.0155 and b = 2.915 in females, and α = 0.0032 and b = 2.976 in males. The von Bertalanffy growth function (VBGF) parameters for sexes combined were Linf = 346.1 mm, k = 0.299 year−1 and t0 = −0.984 years. Longevity (tmax) was estimated at 11.75 years. This study provides valuable data for the stock assessment of M. surmuletus in one of the major Hellenic fishing grounds located in the south Aegean Sea.