Grey Mullets

The aim of this study was to evaluate the effects of a gonadotropin-releasing hormone analogue (GnRHa), administered through injections or with sustained-release implants, on spermiation and sperm quality in thicklip grey mullet, Chelon labrosus. Male broodstock transferred from extensive lagoons were randomly allocated to three treatment groups: (a) weekly saline injections (Saline-INJ), (b) weekly GnRHa injections (10 µg kg-1 bw; GnRHa-INJ), and (c) a single GnRHa EVAc implant (50 µg kg-1 bw; GnRHa-IMP). Males were maintained with females under the same treatment protocols and allowed to spawn. Sperm condition, density, motility, duration of motility, and androgen levels were evaluated weekly at five sampling points (Days 0, 7, 14, 21, and 28). All males exhibited complete spermiation during the first two weeks (Days 0 and 7), followed by a gradual decline throughout the rest of the study (Days 14 and 21). This pattern of decline was not as evident in the groups treated with GnRHa, especially in the GnRHa-INJ group. Sperm density, motility, and motility duration varied strongly over time; however, no significant differences were observed among treatments. GnRHa treatment prolonged the spermiation period and delayed its seasonal decline without significantly altering sperm quality. These results may enable more frequent sperm collection and greater sperm availability, as inferred from the spermiation condition (SCI) and qualitative observations.

The feeding habits of the cichlid Tilapia zillii (Gervais) in Lake Kinneret (Israel) were experimentally studied in indoor glass containers (2.5 hrs) and two trials in outdoor 5 m 3 tanks (20-25 days). The trait of food particle collection by adult fishes was measured. A survey was carried out in the littoral (0-1.0 m deep) zone and fingerlings were sampled by electro-chocker. The gut content of the fingerlings was analyzed. The feeding habits of T. zillii were indicated as planktivorous filtration with more enhancements of small zooplankters (Nauplius, Brachionid rotifers) and fewer of Cladocerans suppressions.

Accepted forpublication Apnl I971 Pseudophoxinus zeregi (Heckel) and 2'. (Pararbodeus) drusensis (Pellegrin) have been examined from populations near their respective type localities. I t was found that there is no basis for the subgenus Pararbodeus and that the two forms are best regarded as subspecies of Pseudophoxinus zeregi. * This work is part of an MSc. thesis in Zoology submitted to Tel-Aviv University. * Ein Fachem, Ein Tanuria and Ein Haririm are small rivulets very close to each other (only a few miles apart) and are connected during the winter.

The University of the Philippines Visaya has developed a Modified Solar Dryer (MSD) facility for improving the quality of dried fish and the technology was extended and transferred to Partido State University. The effectiveness of the dryer was compared to Open Air Dry (OAD), a traditional method of drying. Drying characteristics studies on Split Mullet Fish (Mugil cephalus) brine and different concentrations were conducted using MSD and OAD. The Split fish were dried for 2 days or 16 hours or until the required recommended moisture content of dried fish is reached. The temperature obtained inside and outside the MSD during drying ranges from 31.4 -41.60C and29.7-35.50C respectively. Dryers and brining methods had a significant (p<0.05) on moisture loss and sensory attributes. Brines fish at 10% concentration dried in MSD showed moisture loss (59.23%) It was found that only 12 h of drying is required to bring down to the recommended moisture content of 18-20% for the dried split fish at 10% brine concentration and received highest overall acceptability in the sensory evaluation study.

The cichlid species, Coptodon zillii (Gervais, 1848) is one of the invasive tilapia species, but little is known about its ecological and socio-economic effects on freshwater ecosystems. This study aims to understand socio-economic impacts by considering the ecological roots of the invasion success of C. zillii in one of the internationally important wetlands, Shadegan Wetland in Khuzestan province, southwest of Iran. For this purpose, the impact of the species occurrence on the local fishing communities and the feeding habits of the fish, which may affect the ecosystem of the wetland, were studied from October 2015 to September 2016. The redbelly tilapia has been observed in large numbers in the daily catchment of fishermen and due to its low price, it has greatly decreased their income. Because of the herbivorous diet, redbelly tilapia might cause ecosystem changes that adversely affect the native species, especially the commercially important fish. The unwillingness of fishermen to catch this fish makes it hard to physically remove it and then to control the population growth. Thus, it is possible to reduce its Scientific Reports in Life Sciences 2 (3): 25-38 26 population by using incentives and creating new uses for this species, such as fertilizer production, which for this study presents a new method in this regard.

Conservative morphological characters make identification of mullet species difficult. As a consequence, cosmopolitan distribution of Mugil cephalus is currently under discussion. In order to clarify the controversy regarding the taxonomic status of the southern Atlantic American mullet M. platanus, in relation to Mugil cephalus, a comprehensive analysis is presented using sequences of the mitochondrial gene cytochrome b, landmark-based morphometry and meristic data. The interlandmark distances showed differentiation between individuals of M. platanus and M. cephalus analyzed. Variables, representing the height at different levels of the longitudinal axis of the body, exposed that M. platanus has more robust middle and caudal segments of the body, in a lateral view, with respect to M. cephalus. Transversal series scales have not been useful for the identification of species. Lateral series scales seem to be useful to differentiate species, but taking into account that range showed an overlapped gradual variation. Genetic distance obtained between species shows a typical intrageneric level comparison. Two clear phylogroups have been detected indicating a high degree of genetic isolation between both species. Recognition of M. platanus as valid allopatric species is suggested.

Two species of grey mullets, Liza ramada and Mugil cephalus, are annually introduced in Lake Kinneret (Israel). Both species do not reproduce in the lake. Growth rate of M. cephalus is notably faster than growth rate of L. ramada. Analysis of introduction and commercial catch statistics showed that 27-28% of introduced fish of each species are landed. This information allowed calculating the average specific natural mortality rate (M, year^-1) of both species over the period between their introduction and landing. For L. ramada the M  was -0.39 year^-1 and for M. cephalus the M  was -0.30 year^-1. Computation of economic efficiency of fish introduction, which took into account the species specific growth rate, age structure in catches and market price, showed that M. cephalus has notably greater outcome per similar number of introduced larvae than L. ramada. Potential ecological role of grey mullets in the lake is discussed.

The chapter summarizes current knowledge on fish biology in Lake Kinneret. Nineteen native fish species belonging to six families populate the lake. Three of these species are endemic to the lake and four other species are endemic to the Jordan Valley system. Eight alien species are found in the lake. Four of them are breeding in nature, three can’t breed but are regularly stocked, and one is a hitchhiker that can’t breed. Growth rate equations and weight-length relationships are presented for the dominant cyprinids (Mirogrex terraesanctae, Hypophthalmichthys molitrix, Cyprinus carpio, Barbus longiceps, Capoeta damascina, Carasobarbus canis), cichlids (Oreochromis aureus, Sarotherodon galilaeus, Tilapia zillii, Tristramella simonis), grey mullets (Liza ramada, Mugil cephalus), and catfish (Clarias gariepinus).    The long-term changes in fish community composition in the lake were associated with introduction and invasion of fishes; changes in fishing intensity; modifications of the littoral, and changes of the lake ecological regime. Temporal dynamics, spatial distribution, total abundance and biomass of fish in the lake were studied based on long-term hydroacoustic monitoring. The size structure and abundance of fish in the pelagic zone of the lake display explicit seasonal changes associated with fish spawning migrations and winter-spring recruitment of the dominant bleak M. terraesanctae. Water level fluctuations beyond natural have modified the littoral habitats, which are of specific importance during different life stages of fish. Water level has an immense impact on fish reproduction, survival, recruitment, population dynamics, and eventually determines the catches of commercially important species.
See also chapter: "Fisheries Management"