Identification of grey mullet (Teleostei: Mugilidae) juveniles from British waters

Examination of juveniles (25–50 mm t.l .) of the three species of grey mullet present in British and other nothern European waters has indicated that the melanophore pattern on the ventral surface of the head is a reliable and useful character for identification.     

Age, growth and fecundity of the silver mullet, Mugil curema (Pisces: Mugilidae), in coastal areas of northeastern Venezuela

We studied fecundity and growth in populations of the silver mullet, Mugilcurema, in coastal areas of northeastern Venezuela between March 1992 and July 1993. The average number of oocytes in gonads of 23-42 cm adults was 54 x 10(4), and the relative fecundity was 1,311 oocytes g-1 of fish. The size of mature oocytes did not vary in different portions of the same gonad (p > 0.05) or among the adults in three populations studied. The average egg diameter for adults was 426 microns (CI = 4.34). Age of juveniles, collected from the La Restinga Lagoon at about monthly intervals, from counts of growth lines on the otoliths ranged from 50 to 240 days. The relation of age (number of growth lines) to standard length follows an exponential growth curve. The growth of juveniles varied seasonally and was greatest during the rainy season (April to August), when temperatures were highest. The time of spawning has probably been adapted so that peak recruitment into the lagoons occurs just prior to the rainy season when conditions for growth are most favorable.     

On the structure of retina of a fresh-water mullet, Rhinomugil corsula (Mugilidae, Pisces).

1. The structure of the eye-ball of Rhimomugil corsula has been described. 2. A mid-horizontal ridge (band) along the vitreal surface of the retina in each eye of R. corsula has been observed which divides the retina into a superior and an inferior hemispheres probably adapted for aquatic (dim-light vision) and aerial (bright-light vision) vision. 3. The superior hemisphere has been provided with poorly developed choroid gland and scarce pigment in the pigment epithelial cells. 4. The visual cell layer in the retina of the superior hemisphere contains both single and twin cones. They are alternately arranged in parallel rows. 5. The external and internal limiting membranes have been observed in both the hemispheres under light microscope. 6. The outer plexiform layer of the superior hemisphere contains many horizontal cells arranged into four distinct rows. 7. The inferior hemisphere has a well developed choroid gland, and dense pigment in the pigment epithelial cells.     

Skeletal structure as taxonomic tool for identification of mullet species (Teleostei: Mugilidae) from Aceh waters,Indonesia

Many members of the mullets (family Mugilidae) are very similar morphologically, hence the possibility of taxonomic misidentification. This study involved the use of skeleton structure to distinguish four species of mullets, including Cremugil crenilabis, Liza macrolepis, Moolgarda engelii, and Mugil cephalus, harvested from Aceh waters, Indonesia. The mullets samples were collected from 10 locations, and a total of 10 samples were taken randomly as representatives of each species. The skeletal sample was prepared using the dry method. The results showed the presence of 8 pairs of ribs in C. crenilabis and L. macrolepis, while M. engelii had 9, with 10 in M. cephalus. In addition, the origin of the haemal canal of C. crenilabis is at the 12th vertebrae, extends to the 23rd, while for the other three species it starts at the 10th and extends to the 23rd. In addition, C. crenilabis possesses 12 haemal canals, but the rest have 14. The haemal canal is present in the last precaudal vertebrae of all specimens, except C. crenilabis, whose epural bone in the caudal skeleton is small and located far from the preural, while a larger and distinctly attached form is observed in the rest. Furthermore, L. macrolepis possess a pair of diapophyses, which laterally extend in the 2nd vertebrae. This bone is absent in the three other species. The presence of diapophyses, the number of ribs and haemal canals and the location of the epural bone in the caudal skeleton, and the condition of frontal attachment to the sphenotic are the important characters in distinguishing the four investigated species of mullets.     

The feeding ecology of juvenile mullet (Mugilidae) in south-east African estuaries

Changes in the feeding ecology of juveniles (10–59 mm standard length) of eleven species of Mugilidae were investigated in south-east African estuaries. Adults of all species spawn in the sea and juveniles enter estuaries at a length of about 10 mm. In estuaries they change their feeding habits in the following sequence: zooplankton to zooplankton in the benthos (10–15 mm), zooplankton in the benthos to meiobenthos (10–20 mm), and meiobenthos to sand particles and associated microbenthos (15–25 mm). All species show a similar pattern of change but interspecific competition is probably prevented by the rapid switch to the adult diet of microbenthos and sand particles and because species enter estuaries at different times according to spawning periods. The juveniles seek shallow quiet water areas of estuaries and it is suggested that the change from being planktonic macrophagous carnivores to benthic microphagous omnivores can only take place in the estuaries of the region. Conditions in the inshore waters of the Indian Ocean in south-east Africa are probably too rough for substrate feeding by juvenile mullet.     

A new species of Saturnius Manter, 1969 (Digenea: Hemiuridae) from Mediterranean mullet (Teleostei: Mugilidae)

A new hemiurid digenean, Saturnius gibsoni n. sp., is described from the stomach lining of Mugil cephalus L. off Oran, Mediterranean coast of Algeria. Characteristic morphological features of the new species include small size of the body which is comprised of six pseudosegments, small ventral sucker, weakly developed mound-shaped flange at the level of the ventral sucker, and eggs being large in relation to the size of the body. Saturnius gibsoni n. sp. resembles S. minutus Blasco-Costa, Pankov, Gibson, Balbuena, Raga, Sarabeev & Kostadinova, 2006 and two unidentified Saturnius spp. in the small size of the body and most metrical features. However, in spite of the presence of five transverse septa resulting in six pseudosegments and the range overlap of some metrical features, the ventral sucker in S. minutus is much larger, the ventral sucker muscular flange is more prominent, the last pseudosegment is narrower in relation to body width and more rounded, and the eggs are smaller (mean 21 × 10 vs 25 × 12 μm). Furthermore, the partial sequences of the 28S rRNA gene region (domains D1–D3; 1,195 nt) obtained from two isolates of S. gibsoni n. sp. differed by 11 nt (0.9%) from that of S. minutus. Both unidentified forms of Saturnius are clearly distinguishable from S. gibsoni n. sp. by the presence of six stout, transverse muscular septa, forming seven pseudosegments (vs five septa forming six pseudosegments). Bayesian inference analysis of partial 28S rDNA sequences based on a total of 15 species from the families Hemiuridae and Lecithasteridae depicted the Bunocotylinae Dollfus, 1950 as a strongly supported basal clade, with Bunocotyle progenetica (Markowski, 1936) as the closest sister taxon to Saturnius spp.     

Maturity and fecundity of golden grey mullet (Liza aurata Risso, 1810) in Iranian waters of the Caspian Sea

The objective of the study was to determine some reproductive parameters in the golden grey mullet (Liza aurata Risso, 1810) during two periods half a decade apart while also trying from limited data to identify changes in fecundity over the past half century. Maturity and fecundity of golden grey mullet caught in Iranian waters of the Caspian Sea is not well documented and were thus studied during several seasonal cycles during 2002–2004 to establish basic data on reproduction in the area. The fork length (FL) of 462 sampled fish was between 22.1 and 51.9 cm. The fork length–weight relationship derived from all fish was W = 0.0118FL^2.964. Overall male to female ratio was 1 : 1.42. The reproductive season extended from October to December. Fifty percent of sexual maturity was at FL 26.0 cm. Mature gonads were present in 20% of fish at age 3, 63% at age 4, 88% at age 5, and 97% at age 6. Individual absolute fecundity of the golden grey mullet ranged from 113 386 to 1.47 million eggs, with a mean (±SD) of 451 963 (±274,114.2). An overlap exists between the spawning and fishing seasons. Therefore, the start of the fishing season should be delayed for 1 month in order for stocks to complete their spawning.     

Phylogenetic relationships of nine mullet species (Mugilidae) in the Mediterranean Sea

Phylogenetic relationships among four genera and nine species (Mugil cephalus, Mugil soiuy, Liza ramada, Liza aurata, Liza abu, Liza saliens, Liza carinata, Chelon labrosus, Oedalechilus labeo) of the Mediterranean mullets (Mugilidae) were investigated by means of allozyme electrophoresis using a seven-enzyme system (CK*, GAPDH*, G3PDH*, IDHP*, ME*, MDH*, PGM*) comprising eleven putative loci. The highest genetic divergence was 1.299, detected between M. cephalus and L. aurata and the lowest (0.280) was found between L. carinata and L. saliens. The amount of genetic divergence between the genera Chelon and Oedalechilus did not appear to be high (0.285). In a UPGMA tree, all nine species were grouped in two main branchings. In the first branch, C. labrosus and O. labeo clustered as closest taxa and were sister group to L. ramada. The other four Liza species produced two sub-branching in this group; L. carinata branched together with L. saliens, and L. aurata branched together with L. abu. In the second branch the two species of the genus Mugil, M. cephalus and M. soiuy, clustered together and were clearly isolated from the other three genera.     

The feeding ecology and relative abundance of mullet (Mugilidae) in Natal and Pondoland estuaries

An investigation of the feeding ecology of Mugilidae in Natal and Pondoland estuaries showed that although the diet of the eleven species is similar it varies from one estuary to another and is determined largely by the occurrence of particular food items on substrates of the preferred particle size of each species. The findings of this study support the conclusions reached by Blaber (1976) with regard to the partitioning of the food resource according to inorganic particle size. Particle sizes consumed by each species do not remain the same but vary according to locality. Within any one estuary the mullet species avoid interspecific competition by selecting particles of different sizes. The fish are always graded in the same order with regard to particle size. The relative abundance of the various species of mullet in Natal and Pondoland estuaries is probably not controlled by food or substrate requirements because most species are sufficiently flexible in their feeding ecology to cope with a wide variety of estuarine substrates.     

Genetic relationships of four Taiwan mullets (Pisces: Perciformes: Mugilidae)

Electrophoretic data for 19 presumptive gene loci separated Mugil cephalus from Liza spp. with Nei's genetic distance of 0.863, and from Valamugil formosae with 0.703, and from both Liza and Valamugil with 0.783. Within the genus Liza , Nei's genetic distance was only 0.237 between L. affinis and L. macrolepis.     

Gut ph and digestive strategies in estuarine grey mullet (Mugilidae) and tilapia (Cichlidae)

Tilapia guineensis , which feeds on leafy material, and Sarotherodon melanothron , which utilizes blue-green algae, were both capable of producing a pH 2 or less in the stomach which could contribute to the lysis and digestion of blue-green algae and bacteria. Of the grey mullets investigated, Liza falcipinnis had a gastric pH 3.3–4.5, which may not be low enough to cause cell lysis, whilst Liza dumerili, Mugil cephalus and Mugil curema all had stomach, caecal and intestinal pH's of 7–8.5. Grey mullet appear to have a different digestive strategy to tilapia and may rely upon the establishment of a 'colloid mill' in the stomach.     

New species and new records of Ergasilus Nordmann (Copepoda: Ergasilidae) from the gills of grey mullet (Mugilidae)

Four new Ergasilus species are described from five host species of grey mullet, family Mugilidae, held in the fish collections of The Natural History Museum, London. Ergasilus extensus n. sp. was found on Myxus petardi (Castelnau) from Australia, E. sittangenesis n. sp. on Sicamugil hamiltoni (Day) from Burma, E. piriformis n. sp. on Sicamugil cascasia (Hamilton Buchanan) from India, and E. ecuadorensis n. sp. on Mugil curema Valenciennes and M. hospes Jordan & Culver from Ecuador. New records of E. cyanopictus Caravalho, E. magnicornis Yin, E. orientalis Yamaguti and E. rostralis Ho, Jayarajian & Radhakrishnan on grey mullet are also given.     

The effect of oocytic atresia on fecundity estimates of the rabbit fishSiganus sutor (Pisces: Siganidae) of Kenyan marine inshore waters

In the strongly group-synchronized oocyte development ofSiganus sutor (Valenciennes, 1835) the group of oocytes to be released in the following spawning, is identified. The smallest size of oocyte belonging to this group was identified by the presence of cytoplasmic vacuoles in oocytes in histological sections. These vacuolated oocytes corresponded to oocytes of 150 µm diameter obtained by treatment with Gilson's fixative. The mean number of such oocytes in stage 4 (late developing) ovaries was found to be 638 000. The proportion of these oocytes removed by atresia before spawning was determined on histological sections to be 5%. The corrected estimate of mean fecundity was thus 606 000 oocytes per spawning.     

Cleaning behaviour of the goldsinny (Pisces,Labridae) in Swedish waters

The goldsinny, $\text{Ctenolabrus}$$\text{rupestris}$, on the Swedish west-coast has been shown to be a facultative cleaner with the ballan wrasse, $\text{Labrus}$$\text{berggylta}$, as the cleanee. Twenty-four cleanings were observed during 1975 to 1981. The cleaning pattern of the symbiosis is described and the low rate of cleaners within the species is discussed.     

Parasite prevalence and intensity in Mugil cephalus (Pisces: Mugilidae), from Colorado River, Baja California, Mexico

The parasitic prevalence and mean intensity in the striped mullet, Mugil cephalus, was seasonally determined during an annual cycle (February 1994 to February 1995) in the confluence of the Colorado and Hardy rivers, Baja California, México. Two species of parasites were identified, a nematode, Contracaecum multipapillatum (von Drasche, 1882) (Ascaridida: Anisakidae), and a copepod, Ergasilus versicolor Wilson, 1911 (Poecilostomatoida: Ergasilidae). The larvae of C. multipapillatum, which were represented by two size classes (A and B stages), had prevalences of 30% and 14.5%, respectively; while A. versicolor had a prevalence of 72.7%. The mean intensity of C. multipapillatum was 6.18 and 2.37 individuals per infected fish for A and B stages, respectively; and for A. versicolor, it was of 4.01. The number of parasites (taxa combined) increased with the size of fish (r = 0.22, p = 0.02), but it was independent of the host's condition factor (KSL).