Pellonula Leonensis Research Articles

Food and feeding performance of <i>Pellonula leonensis</i> (Reajon, 1917) (Clupeidae) from Cross River estuary, Nigeria

The diet of Pellonula leonensis was studied in Cross River estuary, Nigeria, from January to December. The major food component were fish larvae, fine particulate organic matter, coarse particulate organic matter (detritus), crustaceans, ants, scales sand and plant matter. Scales and sand were secondary items while macrophyte matters were incidental items. Females had greater feeding activity than males an consumed all the items while males consumed only seven items. The wet season diet comprised 10 items and dry season diet comprised seven items. There was no significant difference in feeding activity in dry and wet seasons. Adult fed more on ants and fish larvae while juveniles fed more on detritus, crustaceans and sand. The observed ontogenetic diet shift enhances co-existence of the size groups. Pellonula was considered piscivorous and cannibalistic its feeding habit. Since it feeds or the same item throughout the years, the food resources were considered important factor in the elimination of the fish population. Keywords: Pellonula leonensis, stomach contents, Nigeria, piscivorous, cannibalistic. AJAZEB Vol. 7 2005: pp. 131-136

English

The abundance of Pellonula leonensis in relation to location, photoperiod, depth, tide, season and gill net selectivity was studied from May 2001 to April, 2002 in the Lower Nun River, Niger Delta. Three sets of gill net with stretched mesh sizes of 8, 12 and 15 mm respectively were used each measuring 35 m in length and 3 m in depth having a surface area of 105 m2. Abundance was least in September and highest in February andP. leonensis was more dominant in the convex area of the river and lowest in the concave section. There was no significant variation (P > 0.05) in abundance of P. leonensis with photoperiod, water depth, tide and season. There was gillnet selectivity with the medium mesh size (12 mm) gill net as more effective constituting 68.77% of the total catch of P. leonensis in the Lower Nun River.   Key words: Abundance, gill net selectivity, Pellonula leonensis, Lower Nun River, Niger Delta.

The structure of anchovy outer retinae (Engraulididae, Clupeiformes) — A comparative light‐ and electron‐microscopic study using museum‐stored material

The outer retinal architecture of Engraulididae is uncommon among vertebrates. In some anchovies, e.g., Anchoa, two cone types are arranged alternating in long photoreceptor chains, i.e., polycones. The cones have radially oriented outer segment lamellae in close contact with a complex guanine tapetum, most probably subserving polarization contrast vision. To clarify the distribution of the aberrant polycone architecture within the Engraulididae and to provide indications about polycone evolution, the outer retina morphology of 16 clupeoid species was investigated by light and electron microscopy, predominantly using museum-stored material. The outgroup representatives of four clupeid subfamilies (Clupeonella cultriventris, Dorosoma cepedianum, Ethmalosa fimbriata, Pellonula leonensis) show a row pattern of double cones, partially with single cones at defined positions and a pigment epithelium with lobopodial protrusions containing melanin. The pristigasterid Ilisha africana has double rows of single cones lying between linear curtains of pigment epithelium processes filled with minute crystallites and melanin concentrated near their vitreal tips. Within the Engraulididae, two main architectures are found: Coilia nasus and Thryssa setirostris have linear multiple cones or polycones separated by long pigment epithelium barriers containing tapetal crystallites and melanin in the tips (also found in Setipinna taty), whereas Anchoviella alleni, Encrasicholina heteroloba, Engraulis encrasicolus, Engraulis mordax, Lycengraulis batesii, and Stolephorus indicus exhibit the typical polycone architecture. Cetengraulis mysticetus and Lycothrissa crocodilus show cone patterns and pigment epithelium morphology differing from the other anchovy species. The sets of characters are compared, corroborated with the previous knowledge on clupeoid retinae and discussed in terms of functional morphology and visual ecology. A scenario on polycone evolution is developed that may serve as an aid for the reconstruction of engraulidid phylogeny. Furthermore, this study demonstrates the suitability of museum material for morphological studies, even at the electron microscopic level.

Studies On The Atalla Fishery Of The Lower Anambra River, Nigeria

The atalla lift net fishery of the lower Anambra river was investigated from May, 1998 to March, 1999 by sampling commercial fishers' catches and obtaining from fishers information relating to fishing time, catch, income and preservation of catch. The species composition of the total catch showed that there were 40 species of fin fish, two decapod crustaceans and a mollusc. Pellonula leonensis was the most abundant fish species by number and weight followed by Parailia pellucida. P. leonensis and P. pellucida exhibited inverse numerical relationship. The target clupeids and schilbeids constituted over 68% and 55% by number and weight respectively of the overall catch. A total of 23 atalla fishing units operated in the lower Anambra river and over 91% of them were operated by Ijaw migrant fishers. The net of atalla was made up of two ply and 10 mm mesh size or plastic mosquito gauze. The canoe was planked and there was a close relationship between the base of the atalla lift net and the length of the canoe (r2=0.91). The total annual catch was estimated at 155 t excluding the quantity consumed by the fishers' families. Smoking was the main method of preservation. It took 2±0.04 days to dry a batch of elem and smoked fish were packaged in small baskets lined with cement paper. Atalla fishery appeared not to be detrimental to the fisheries of the relatively large-sized fish species and it should be encouraged to harvest the abundant clupeids and schilbeids in the mixed species fishery of the lower Anambra river. Mesh regulation is not relevant in the management of atalla fishery. Key Words: Atalla fishery, catch, species composition, abundance, preservation, Anambra river Bio-Research Vol.2(1) 2004: 82-90

The Biology of <i>Pellonula leonensis</i> Boulenger, 1916 (Osteichthyes: Clupeidae) in Anambra River, Nigeria

The biology of the commercially important clupeid, Pellonula leonensis, was studied from May 1998 to March 1999 in the Anambra river. In the atalla fishery of this river, the clupeid was the dominant species in terms of number and weight. Total length (TL) ranged from 3.4 to 8.5 cm and weight from 0.3 to 4.6 g; males were not longer or heavier than females. The mean exponent (b = 2.66) of the length-weight relationships of 12 populations indicated negative allometric function. Mean monthly Fulton's condition (K) was not dependent on season. There was little variability in the mean monthly gonadosomatic index (GSI) and breeding occurred throughout the year. Maturity occurred earlier in males than females; 50% of both sexes matured at 4.7 cm TL. Fecundity ranged from 126 to 1580 oocytes (mean 896 ± 477 oocytes). Total length was a better predictor of fecundity than ovary weight. Index of food significance (IFS) showed that Insecta (51:67%) was the dominant food group, followed by Algae (15.66%) and plant detritus (8.02%). Food items of primary importance were Ephemeroptera nymphs, Chironomidae, unidentified insects, fish, Microcystis, plant detritus and sand grains. Food richness and diet breadth were dependent on season. Key Words: Pellonula, Leonensis, Anambra River Bio-Research Vol.1(2) 2003: 33-50