Solid-State Hydrolysis (SSH) Improves the Nutritional Value of Plant Ingredients in the Diet of Mugil cephalus

The possibility of improving the nutritional quality of plant byproducts (brewers’ spent grain and rice bran) through an enzyme treatment was tested in a formulated feed for grey mullet (Mugil cephalus). The enzyme treatment was carried out by Solid-State Hydrolysis (SSH) using a commercial preparation including carbohydrases and phytase. A feed prepared without the treatment and a commercial feed for carp were used as controls. In a preliminary short-term trial carried out at laboratory facilities, fish receiving the enzyme-treated feed showed significant improvement in both FCR and SGR when compared to those obtained with the untreated diet, although both experimental diets presented worse values than those obtained with the commercial feed. Different metabolic indicators including higher values of muscle glycogen and plasmatic triglycerides supported the positive effect of the enzyme treatment on the nutritional condition of the fish over those fed on the diet containing non-treated ingredients. Results of growth and feed efficiency that were obtained in a second long-term trial developed for 148 days under real production conditions evidenced the equivalence among the experimental and commercial diets and confirmed that enzyme pretreatment of plant ingredients by SSH may be a useful procedure to improve the nutritive value of high fiber plant byproducts when included in practical diets for this species and others with similar nutritional features.

Population genetic structure and connectivity patterns of the kanae (Mugil cephalus) in New Zealand inland and coastal waters

<p>Mugil cephalus is a cosmopolitan fish species found in most coastal waters from tropical to temperate zones. It is a species common in the near-shore marine environment, and known to reside in estuarine and freshwater systems. Adult M. cephalus move out to sea to spawn in aggregations. Their larvae can drift on surface ocean currents for over a month before recruitment to nursery grounds. Mugil cephalus is a species that is closely associated with the coastal environment, but it is capable of interoceanic migrations. Population genetic studies have reported high levels of genetic differentiation among populations in the Mediterranean, Atlantic and western Pacific. However, there is no evidence to suggest reproductive incompatibility has arisen among populations. In New Zealand M. cephalus supports important recreational, commercial and customary fisheries, but very little is known about the distribution and connectivity among populations. The aim of this study was to use nuclear microsatellite DNA (msatDNA) and mitochondrial DNA (mtDNA) markers to describe the population genetic structure, connectivity patterns and to determine the phylogeographic history of New Zealand M. cephalus populations. Total of 850 samples were collected (576 adults and 274 juveniles) during the summers of 2010 and 2014-2015 from 15 locations around coastal and inland waters of the North Island, and one location in Marlborough Sounds. In addition, 245 mtDNA sequences were added from previously published studies and used to outgroup the New Zealand population and place it into the context of the other Pacific populations. Seven msatDNA loci were isolated and used to determine the population genetic structure and connectivity patterns of M. cephalus in New Zealand. Admixture of four genetically distinct groups or populations was identified and a chaotic spatial distribution of allele frequencies. Within each population there was significant gene flow among locations, no pattern of genetic isolation-by-distance was identified and there was a high proportion of non-migrant individuals. There was evidence of bottlenecks and seasonal reproductive variation of adults, which could explain the significant shifts in the effective population size among locations. To test whether the pattern of genetic variation in M. cephalus populations was the result of seasonal variability in the reproductive success of adults, DNA from adult and juvenile samples were used to test for differences in the levels of genetic variation between generations (cohorts). Juveniles were grouped by age classes and compared to the adults. The levels of genetic diversity within the groups of juveniles were compared to the adult population and significant genetic bottlenecks between juveniles and adults were detected. This pattern was consistent with the Sweepstake-Reproductive-Success hypothesis. Two spawning groups in the adults were identified, an early spawning group and a late spawning group. The analysis of DNA sequence data from the mtDNA Cytochrome Oxidase subunit 1 (COX1) gene and D-loop region showed two sympatric haplogroups of M. cephalus. New Zealand was most likely colonised by M. cephalus migrants from different population sources from the Pacific first ~50,000 and a second wave of migrants from Australia between ~20, 000 and ~16,000 years ago. High levels of gene flow were detected, but there has not been enough time for genetic drift to completely sort the lineages. The findings of this thesis research will help with the understanding of aspects of M. cephalus dispersal and the genetic structure of populations. The patterns of connectivity can be used to better align the natural boundaries of wild populations to the fishery management stock structure. Understanding the reproductive units, levels of genetic diversity and the patterns of reproduction of M. cephalus will assist management efforts to focus on the key habitats threats, risks and the long-term sustainability of the species.</p>

Population genetic structure and connectivity patterns of the kanae (Mugil cephalus) in New Zealand inland and coastal waters

<p>Mugil cephalus is a cosmopolitan fish species found in most coastal waters from tropical to temperate zones. It is a species common in the near-shore marine environment, and known to reside in estuarine and freshwater systems. Adult M. cephalus move out to sea to spawn in aggregations. Their larvae can drift on surface ocean currents for over a month before recruitment to nursery grounds. Mugil cephalus is a species that is closely associated with the coastal environment, but it is capable of interoceanic migrations. Population genetic studies have reported high levels of genetic differentiation among populations in the Mediterranean, Atlantic and western Pacific. However, there is no evidence to suggest reproductive incompatibility has arisen among populations. In New Zealand M. cephalus supports important recreational, commercial and customary fisheries, but very little is known about the distribution and connectivity among populations. The aim of this study was to use nuclear microsatellite DNA (msatDNA) and mitochondrial DNA (mtDNA) markers to describe the population genetic structure, connectivity patterns and to determine the phylogeographic history of New Zealand M. cephalus populations. Total of 850 samples were collected (576 adults and 274 juveniles) during the summers of 2010 and 2014-2015 from 15 locations around coastal and inland waters of the North Island, and one location in Marlborough Sounds. In addition, 245 mtDNA sequences were added from previously published studies and used to outgroup the New Zealand population and place it into the context of the other Pacific populations. Seven msatDNA loci were isolated and used to determine the population genetic structure and connectivity patterns of M. cephalus in New Zealand. Admixture of four genetically distinct groups or populations was identified and a chaotic spatial distribution of allele frequencies. Within each population there was significant gene flow among locations, no pattern of genetic isolation-by-distance was identified and there was a high proportion of non-migrant individuals. There was evidence of bottlenecks and seasonal reproductive variation of adults, which could explain the significant shifts in the effective population size among locations. To test whether the pattern of genetic variation in M. cephalus populations was the result of seasonal variability in the reproductive success of adults, DNA from adult and juvenile samples were used to test for differences in the levels of genetic variation between generations (cohorts). Juveniles were grouped by age classes and compared to the adults. The levels of genetic diversity within the groups of juveniles were compared to the adult population and significant genetic bottlenecks between juveniles and adults were detected. This pattern was consistent with the Sweepstake-Reproductive-Success hypothesis. Two spawning groups in the adults were identified, an early spawning group and a late spawning group. The analysis of DNA sequence data from the mtDNA Cytochrome Oxidase subunit 1 (COX1) gene and D-loop region showed two sympatric haplogroups of M. cephalus. New Zealand was most likely colonised by M. cephalus migrants from different population sources from the Pacific first ~50,000 and a second wave of migrants from Australia between ~20, 000 and ~16,000 years ago. High levels of gene flow were detected, but there has not been enough time for genetic drift to completely sort the lineages. The findings of this thesis research will help with the understanding of aspects of M. cephalus dispersal and the genetic structure of populations. The patterns of connectivity can be used to better align the natural boundaries of wild populations to the fishery management stock structure. Understanding the reproductive units, levels of genetic diversity and the patterns of reproduction of M. cephalus will assist management efforts to focus on the key habitats threats, risks and the long-term sustainability of the species.</p>

Weight-length relationship and condition factor of Mugil cephalus (Linnaeus 1758, Mugilidea) in the special wildlife reserve of Gueumbeul (RSFG) in Senegal

The weight-length relationship and the condition factors are fundamental parameters with several uses in biology, fish ecology and fisheries management. Thus, in the Special Wildlife Reserve of Gueumbeul (SWRG) in Senegal, the weight-length relationship and condition factor were established for Mugil cephalus (Linnaeus 1758). A total of 311 individuals (97 females and 214 males) of M. cephalus were collected by the artisanal fishery using cast nets. The total length and weight ranged from 11.1 to 25 cm and 15.9 to 145.26 g, respectively. The results showed that in the SWRG, both in females (b = 2.60) and males (b = 2.899), M. cephalus had negative allometric growth. The analysis of variance showed no significant difference (p > 0.05) in the coefficients of determination between females (R = 0.96) and males (R = 0.84). Condition factors (K) were 3.07 and 1.23 for males and females respectively for M. cephalus in the reserve.

Recombinant Fsh and Lh therapy for spawning induction of previtellogenic and early spermatogenic arrested teleost, the flathead grey mullet (Mugil cephalus)

With the expansion and diversification of global aquaculture, efforts continue to develop new bio-technologies for assisted reproduction in species that present reproductive dysfunctions. Flathead grey mullet (Mugil cephalus) held in intensive conditions in the Mediterranean region, display a severe reproductive dysfunction, where males do not produce fluent milt and females are arrested at previtellogenesis or early stages of vitellogenesis. In the present study, weekly injections of species-specific single-chain recombinant gonadotropins (rGths); follicle stimulating hormone (rFsh) (6 to 12 μg kg-1 doses) and luteinizing hormone (rLh) (2.5 to 24 μg kg-1 doses) were administered to induce vitellogenesis, from previtellogenesis / early vitellogenesis to the completion of vitellogenic growth in females and enhance spermatogenesis to produce adequate volumes of sperm from non-fluent males. During the experiment, all treated females (n = 21) developed oocytes in late vitellogenesis with 603 ± 8 μm diameter and all treated males produced fluent sperm. To induce oocyte maturation, ovulation and spawning, females were treated with either (i) a priming dose of 30 μg kg-1 of rLh and a resolving dose of 40 mg kg-1 of progesterone (P4), (ii) priming and resolving doses of 30 μg kg-1 of rLh, or (iii) priming and resolving doses of 40 mg kg-1 of P4 given 24:05 ± 0:40 h apart. Females were placed in spawning tanks with rGth treated males that had fluent sperm. Spontaneous spawns of fertilised eggs were obtained after inducing with rLh + P4 or rLh + rLh (priming and resolving injections) with a spawning success of the 85% (8 of 9 females) and 100% (n = 6), respectively. The eggs collected from the tanks presented 64 ± 22% fertilization with embryo development and 57 ± 24 % hatching. The treatment P4 + P4 had a lower ovulation success (50 % - 3 of 6 females) and spawning success (17 %) with no fertilised eggs. Success was independent of the initial gonadal stage of females. In comparison, control females did not show any advance in gonadal development from initial stages and control males did not produce fluent sperm. The present results confirm the possibility of controlling oogenesis from previtellogenesis to the completion of maturation and fertilised tank spawning using exclusively rFsh and rLh in a teleost species.