Liza Dumerili Research Articles

Reproduction of five mullet fish (Mugilidae) in Grand-Lahou Lagoon, Côte d’Ivoire: Size at first sexual maturity, reproduction period and sex ratio

This work provides information on Mugilidae fish reproduction in Grand-Lahou lagoon. From September 2009 to August 2011, for each specimen sampled, the total length in cm, the total mass and the eviscerated mass in g, the gonads mass in cg, the sex and the gonads maturity stages were recorded. Parameters studied were size at first sexual maturity, reproduction period and sex ratio. The sexual maturity is reached between 16.1 cm and 21.0 cm in four of the five species studied and at 41.6 cm in Mugil cephalus females. Liza dumerili and Mugil curema reproduce from September to November, Liza falcipinnis from July to October, Mugil bananensis from March to June and Mugil cephalus from August. These species reproduce in lagoon, except Mugil cephalus. During breeding season, the sex ratio is in favour of females in Mugil curema and Mugil bananensis. In Liza dumerili and Liza falcipinnis, sexes are rather balanced.

Eco-Morphological Patterns and Diversity of Some Fishes from the Ogu River in Rivers State, Niger Delta, Nigeria

Aim: Eco-morphological studies show that morphological traits are adaptive, which means that traits evolve and change as a result of the activities going on in the environment such as predation, competition, and other biotic associations. This study was taken to determine the eco-morphological patterns of some fishes from the Ogu River in Ogu/Bolo Local Government Area of Rivers State, Niger Delta, Nigeria.
 Study Design: Field work and random sampling.
 Place and Duration: Three stations were sampled along the Ogu river and the duration of the study was four months (January- April 2018).
 Methodology: A total of 193 individual fishes were caught, comprising of 5 families and 11 species. Fish samples were obtained with the aid of a seine net; identified, weighed and morphometric measurements were made, to provide the eco-morphological attributes. Fishes were dissected to measure intestinal length. Statistical analysis includes Principal Component Analysis (PCA) of morphometric ratios and intestinal length - total length ratios of fish.
 Results: The fish species found were Tilapia guineensis, Tilapia zilli, Mugil bananensis, Mugil curema, Liza falcipinnis, Liza dumerili, Liza grandisquamis, Pomadasys rogerii, Pomadasys jubelini, Lutjanus endecacanthus and Eucinostomus melanopterus. Tilapia guineensis was the most abundant species, Shannon Weiner diversity index (H) ranged from 1.83 - 1.96, Simpson’s dominance index ranged from 0.79 - 0.85. The PCA analysis using different morphological attributes revealed 4 groups in feeding regime (omnivorous - Mugilids; herbivorous - Cichlids; larger carnivores - Lutjanids and smaller carnivores - Pomadasyids), and 3 groups in the fishes habitat preference in water as (1: Cichlids, 2: Mugilids and 3: Pomadasyids, Lutjanids and Gerreids).
 Conclusion: This study revealed morphometric attributes of some fishes of the Ogu river in Rivers State Nigeria and their relation with feeding, microhabitat and environmental parameters.

Eelgrass beds and bare substrata – sparid and mugilid composition in contrasting littoral estuarine habitats

Seagrass beds serve as nursery grounds for many fish species and often play an important role in the juvenile stages of economically and recreationally important fishes. The eelgrass Zostera capensis is the dominant submerged macrophyte in permanently open South African estuaries and occupies large intertidal and subtidal areas within the Knysna system. The primary objective of this study was to compare the occurrence of sparids and mugilids in eelgrass and nearby bare sediment areas using sampling with seine nets. The hypothesis that was tested is that mugilids are dominant in unvegetated areas of the Knysna Estuary littoral whereas sparids predominate within eelgrass beds located in the same zone. The results indicate that the family Mugilidae is better represented at unvegetated sites when compared to members of the family Sparidae, with the exception of Lithognathus lithognathus, but that the dominant three sparids and dominant two mugilids were most abundant in sparse eelgrass beds that included both bare and vegetated areas within this habitat type. The main fish species responsible for the separation of fish assemblages associated with unvegetated sites versus those associated with vegetated areas were Rhabdosargus holubi, Liza dumerili, Liza richardsonii, Lithognathus lithognathus, Sarpa salpa and Diplodus capensis, with R. holubi, S. salpa and D. capensis being mainly attracted to eelgrass habitats and L. dumerili, L. richardsonii and L. lithognathus having a stronger affinity for bare areas. This finding confirms a previous estuarine study in the nearby Swartvlei lake littoral, which found that sparids dominated areas where aquatic macrophytes were extensive and that mugilids became more prevalent at those same sites when the macrophytes underwent complete senescence. The length-frequency distributions of some sparid and mugilid species differed considerably between eelgrass and bare sediment areas, whereas those of other species showed little or no difference between these two habitat types.

Effect of a marine protected area on tropical estuarine fish assemblages: Comparison between protected and unprotected sites in Senegal

A comparative study of fish assemblages of a marine protected area and an exploited area was carried out in the Sine Saloum estuary (Senegal, West Africa). Data were collected at these two sites between 2008 and 2011. The two areas are morphologically similar, and comparison of the physicochemical parameters (salinity, transparency, temperature and percentage of saturation of dissolved oxygen) showed that the water masses are similar. The bio-ecological indicators and ecological, trophic and size structures were also compared. Given the environmental similarity of the two sites, their differences in bio-ecological characteristics and fish assemblage organization can be explained by the protection status of the MPA. The species richness and fish abundance per sampling unit were higher in the exploited site, but the mean trophic level and the observed maximum size of individuals were higher in the MPA. Although slightly higher for the MPA, the differences observed for biomass and average size between the two sites were not significant. The beta diversity in the MPA was higher than in the exploited site. The fish assemblage was dominated in terms of abundance by two pelagic herbivores Ethmalosa fimbriata (80%) and Sardinella maderensis (12.3%) and in terms of biomass by E. fimbriata (37.4%) and a benthic predator, Arius latiscutatus (23.7%). The assemblage of the MPA had a marine affinity characterized by the presence of piscivorous or generalist predators; large individuals were not uncommon. In the exploited site, the fish assemblage was relatively stable, dominated in abundance by E. fimbriata (33.4%) and S. maderensis (32.8%). In terms of biomass, a species of mullet, Liza dumerili, ranked first (26.2%), followed by E. fimbriata (22.4%) and S. maderensis (14.9%). The assemblage in the exploited site had a more estuarine affinity, dominated by detritivorous or phytophagous herbivores. Individuals observed there were mostly of small or medium size. This study confirms that the establishment of MPA is an effective tool for restoring marine biodiversity and trophic structure of fish assemblages.

Recruitment patterns of young-of-the-year mugilid fishes in a West African estuary impacted by climate change

With the persistence of the sub-Saharan drought since the 1970s, the Sine Saloum estuary (Senegal) – the second largest coastal Biosphere Reserve of West-Africa – has become an “inverse estuary” and hypersaline (salinity > 60) in its upstream part. A one-year survey was conducted from April 2007 to March 2008 at eight sites distributed along the salinity gradient, to investigate the recruitment patterns of young-of-the-year mugilids in such an impacted ecosystem. Fishes were sampled monthly with a conical net and a beach seine in salinities ranging from 31 to 104. Samples were identified to the species level. For the smallest individuals (<20 mm SL) a PCR–RFLP technique, developed on the mitochondrial 16S ribosomal RNA region, was used for identification. A total of 8438 juveniles belonging to six of the eight species of mugilids known for the tropical Eastern Atlantic were collected: Mugil bananensis, Mugil cephalus, Mugil curema, Liza dumerili, Liza falcipinnis and Liza grandisquamis. One species, L. dumerili, represented 89% of the total catch. Length–frequency distributions revealed that M. cephalus and L. dumerili preferentially recruited during the dry season whereas the recruitment of M. curema, M. bananensis and L. falcipinnis generally occurred during the wet season. Minimal size at recruitment ranged from 9 to 19 mm SL depending on the species, the smallest size being that of L. dumerili. Despite the general salinity increase in the estuary, most parts of the Sine Saloum were suitable for the juveniles. Only the hypersaline area in the uppermost part of the estuary presented very low fish abundance for all species. According to the species, small recruits (12–20 mm SL) were collected at salinities up to 47–78, suggesting that osmoregulatory capacities had been gained early during ontogenesis, possibly resulting from an adaptation of these populations to changing environmental conditions.

Status of the estuarine fish fauna in the St Lucia Estuarine System, South Africa, after 30 months of mouth closure

The Lake St Lucia Estuarine System, South Africa, has been under pressure due to recent drought conditions, which led to extreme low lake levels, hypersaline conditions and closure of the mouth. The estuary mouth closed in June 2002 and has remained so for more than two-and-a-half years. A lack of information on biotic responses during extended closed-mouth conditions prompted a study to ascertain the current status of the fish fauna in the system. Fish were sampled with seine and gill-nets at six sites spread throughout the system. At the time of sampling in December 2004, the system had become partitioned into four isolated compartments. A total of 4 475 fish comprising 30 species were recorded during the survey. The CPUEs were generally low, except for those of Oreochromis mossambicus, Liza dumerili and Ambassis ambassis. The freshwater cichlid O. mossambicus made up 45% of the total catch. The species composition in each of the four compartments of the system were very different. Historical data indicated a loss of about 40% of the commonly-occurring species from the lake since mouth closure, reflecting a substantial change in species composition from that which occurs under 'normal' conditions. It is expected that the decline in the number of species and the abundance of remaining taxa will continue if drought conditions persist and the mouth remains closed.

The sublethal effects of copper and lead on the haematology and acid-base balance of the groovy mullet, Liza dumerili

Toxicity bioassays were conducted on groovy mullet, Liza dumerili, using copper and lead, in order to assess how these metals affected their blood haematology and acid-base balance. Short-term (96 hours) exposure to lead caused significantly more haematological response [PCO2] than copper, when compared to the control. When copper and lead were applied in combination there were significant increases in bicarbonate content and red blood cell count of the fish. Long-term (28 days) exposure to copper and lead resulted in significant increases in blood glucose, haemoglobin content and the acid-base status of the fish. The results of this study highlight the stress to which estuarine fish are exposed through the uncontrolled discharge of heavy metals and the inherent dangers posed by combinations of metals in the aquatic environment. They will also help emphasise the need to control pollution in order to protect aquatic biodiversity.

Seasonal Abundance Distribution and Catch Per Unit Effort of Fishes in the Swartkops Estuary

Catch per unit effort was obtained for the nekton of the Swartkops estuary near Port Elizabeth by means of gill netting. Fifty gill net catches were made in which 1 269 fish were caught in areas representative of the mouth, middle and upper reaches of the estuary. Pomadasys commersonni, already shown to be the most abundant angling species in the estuary, dominated gill net catches both in terms of mass (29%) and numbers (17%). The family Mugilidae (five species) comprised 25% of the mass and 42% of the numbers caught. Environmental factors and availability of food that might determine distribution offish in the estuary are discussed. The largest mean mass per individual was found in Chanos chanos (4 473 g), Elops machnata (1 656 g) and Valamugil buchanani (1 580 g). Lowest mean masses were recorded for Monodactylus falciformis (63 g), Rhabdosargus holubi (88 g) and Liza dumerili (94 g).

Routine oxygen consumption of Mugil cephalus, Liza dumerili and L. richardsoni at Different temperatures and salinities

Oxygen consumption studies were undertaken with 3 mullet species to determine b, the exponent of w, as well as a, as indices of metabolic rate in the equation M=awbwhere M=metabolic rate, a=the intensity of metabolism, W=body weight, and b=the exponent of w. This was done under 5 experimental temperatures (13°, 18°, 23°, 28°, 33°C) for Mugil cephalus and Liza dumerili at 1 and at 35‰ S, and for L. richardsoni at 35‰S only. Mean b values were approximately 0.85. The a values depended on temperature, and increased according to Van't Hoff's law except for L. dumerili (1‰ S) and L. richardsoni (35‰ S) for a temperature increase from 23° to 28°C. It was found that handling had a profound influence on metabolic rate and led to considerably increased consumption rates during the first 8 h after introduction into the respiration chambers. Fasting in L. dumerili resulted in a total drop of 27% in oxygen consumption over a period of 6 days, of which 10% occurred over the first 24 h. Oxygen consumption displayed diurnal rhythms during the 6 day period, with lowest consumption rates at midday and midnight and highest just after sunrise and sunset.

A Simple Method For The Preparation Of Sperm Of External Fertilizers For Scanning Electron Microscopy

A simple technique is described for the study of sperm of some external fertilizers (sea urchin, Parechinus angulosus; teleost, Liza dumerili; anurans, Xenopus laevis and Bufo rangeri) by means of scanning electron microscopy. The technique involves: (i) dilution of sperm with water of the natural environment of the animals or artificial media resembling their natural environment; (ii) spreading of sperm suspension on 10-mm square Perspex plates; (iii) fixation of diluted sperm with 2.5 pH 7.4 Millonig phosphate buffered glutaraldehyde (1 hour); (iv) repeated washing in phosphate buffer, air drying and coating with palladium-gold in a vacuum evaporator. Postfixation with 1% osmium tetroxide did not improve the results and dehydration with an alcohol series was not necessary.

The Structure of the Testis of the Mullet,Liza Dumerili(Teleostei; Mugilidae) With Special Reference to Spermatogenesis

The macro-morphology and the histology of the testis of Liza dumerili are described with special reference to the various types of spermatogenic cells. L, dumerili possesses typical teleost testes. The only peculiarity is the conspicuous main sperm duct, which runs on the surface (medio-ventral) along the entire length of each testis. Testicular lobules contain cysts in which highly synchronized spermatogenesis takes place. Three generations of spermatogonia are evident, although further subdivisions are possible. Four types of primary spermatocytes are recognized. Typical interlobular Leydig cells appear in close association with small blood vessels. “Lobule-boundary cells” seem to be present but were only evident in I µm Epon sections.

The Structure of the Spermatozoon of Liza Dumerili (Teleostei) With Notes on Spermiogenesis

AbstractThe structure of the sperm of Liza dumerili was studied by light microscopy and scanning and transmission electron microscopy.The sperm have a kidney-shaped nucleus. The “hilus” faces posteriorly and the proximal centriole is situated within the nuclear pit. Nuclear rotation takes place during spermiogenesis and the sperm are therefore related to those of other teleosts showing Type I spermiogenesis. No acrosome is evident. The midpiece is small but distinct and contains four spherical mitochondria. The flagellum enters the midpiece eccentrically and the axoneme runs obliquely towards the distal centriole to which it is connected. The flagellum conforms to the 9 + 2 flagellar pattern.

The Breeding Cycle of MaleLiza Dumerili(Teleostei: Mugilidae) in the Mouth of the Swartkops Estuary

The breeding cycle of male Liza dumerili was studied in the Swartkops Estuary using a visual index, a gonosomatic index and a histological index. Histological studies were superior to any other means of establishing the breeding cycle in detail. Male fish were in the inactive or non-breeding state during the winter months. During early spring the gonads started to mature and full ripeness was attained during December and January. January and February were the main spawning months, and in addition a short spawning peak might be present during October. The seasonal appearance of spermatogonia in the testes is discussed.

Chemical composition of alimentary canal contents of mullet (Teleostei: Mugilidae) caught in the Swartkops Estuary near Port Elizabeth, South Africa

Composition of alimentary canal contents (protein, ash, moisture and carbohydrate by difference) of four mullet species from the Swartkops Estuary, were determined monthly over a 13-month period. It was found that Liza tricuspidens consumed the most nutritious (highest protein and carbohydrate and lowest ash) material followed by Mugil cephalus, Liza richardsoni and lastly Liza dumerili, the most abundant mullet species in the estuary. It was also found that smaller specimens, irrespective of species, consumed the most nutritious food material. An attempt was made to relate chemical composition to the particular food and substrate preference of each species. Correlation coefficients between moisture and protein (positive), moisture and ash (negative) and ash and protein (negative) enabled the calculation of regression equations by which protein and ash can be determined from a relatively simple moisture determination.

Body composition of Mugil cephalus, Liza dumerili, Liza richardsoni and Liza tricuspidens (Teleostei: Mugilidae) caught in the Swartkops Estuary

Body composition (protein, fat, ash and moisture) and energy content of four mullet species Mugil cephalus, Liza dumerili, Liza richardsoni and Liza tricuspidens were determined monthly for 13 months in specimens taken from the Swartkops Estuary. Six size classes (<2.5, 2.6–6.0, 6.1–10.0, 10.1–15.0, 15.1–23.0 and > 23 cm SL) were analysed separately. Statistical analyses of results could only be performed on three size classes of M. cephalus, L. dumerili and L. richardsoni due to inavailability of fish during certain months. Regression equations were calculated for those body components that were significantly correlated, viz.: energy and moisture, fat and moisture, protein and moisture and energy and fat. The influence of species, size as well as seasonal effects and reproductive cycle on body composition were investigated. It was found that in general Liza dumerili had the lowest mean body energy and fat values and Liza tricuspidens the highest. Smaller size fish were lower in energy and fat and larger size fish lower in moisture. Overall mean values showed that body energy reserves were the highest during the winter. Sexually mature specimens of Liza dumerili showed a build-up of energy before the commencement of the spawning season.

Stomach Content Analyses of Mullet from the Swartkops Estuary

The stomach content of four species of mullet (Mugil cephalus, Liza dumerili, Liza richardsonii and Liza tricuspidens), was analyzed. The nature of the stomach content gave some indication of the areas in which each species of mullet had been feeding, the type of substratum from which each had been feeding and the diatom species which each ate.