The head-body weight and head-body length relationship of Synodontis schall (Bloch and Schneider 1801) in Asa Lake, Ilorin, Nigeria

A total of 710 specimens of Synodontis schall were analyzed for the head body weight and head body length relationship. The head constituted 40% of the total body weight and 30% of the total body length. The mean head weight for male and female computed was 23.90g and 29.13g respectively. Head weight in both male and female was significantly different (P<0.01) while the head length for the combined sexes showed no significant difference (P>0.05). Fat accumulation in the body tissue was prominent in the females than males usually before the breeding season. The significance of the cephalo-nuchal shield in the bony head of Synodontis species compared with some other catfishes in the lake was also discussed

The relationship between some physicochemical parameters and plankton composition on fish production in ponds

The effect of physico-chemical parameters and plankton composition on fish production in ponds was investigated in six fish farms for eight weeks. The physicochemical parameters investigated were temperature=25-30 plus or minus C, transparency=0.45-0.57m, dissolved oxygen=3.0-10.9mg/l, pH=6.0-7.7, dissolved carbon dioxide=5.46-28.3mg/l, total alkalinity=44.37-80.0ppm, chemical oxygen demand=31.88-72.18mg/l and biological oxygen demand=0.66-48.34mg/l. Plankton composition varies and was made of four families of phytoplankton namely; Cyanophyceae, Chlorophyceae, Dinophyceae and Diatomida; and four families of zooplankton viz; Protozoa, Rotifera, Copepoda and Dinoflagellates. Farm 1 and 6 recorded the highest average weight of about 1.0kg and average total length of about 40.0cm for the two fish species. This study showed that fish yield was dependable on the quality and management of pond water characteristics

Relationship between the basic morphometric measurements and growth pattern of Heterotis niloticus from River Kaduna floodplain

A total of 61 specimens of Heterotis niloticus were evaluated by linear regression and correlation. The specimens had mean standard length of 27.09 plus or minus 4.73cm, total length of 33-49cm, mean weight of 2445,108.3g, mean snout length of 48 plus or minus 0.86cm, mean eye diameter of 1.30 plus or minus 0.15cm, mean head length of 6.29 plus or minus 1.75cm. There was a strong relationship between the length and the weight, the eye diameter and the standard length, snout length and the standard length, head length and the standard length, snout length and the weight, head length and the weight (P<0.05). But the correlation of the eye diameters and the weight was insignificant (P>0.05). The growth pattern analysis depicts that the growth was negatively allometric with a b value of 1.16

Fishery resource surveys: beyond length-weight relationship models

Fisheries resource surveys are regular management tools for rational exploitation of commercial fisheries. In a growing number of cases, the use of these resource surveys has been largely restricted to assessment of the relative well being of fish stocks and the potential yields of such fisheries. This paper seeks to demonstrate that the data from such surveys can also be easily used to evaluate species diversity of such fisheries, both in terms of species richness and equitability of distribution. Using published data on two freshwater and two marine fisheries as case studies, Shannon-Wiener Diversity Function and Simpson's Index were computed for each of these fisheries. These biodiversity indices gave a deeper insight into the environmental status of each of these fisheries, beyond what the length-weight relationship models can reveal. Generally, while the marine fisheries showed more species richness, the freshwater fisheries apparently had more stable and equilibrated fish communities

The relationship between some physicochemical parameters and plankton composition on fish production in ponds

The effect of physico-chemical parameters and plankton composition on fish production in ponds was investigated in six fish farms for eight weeks. The physicochemical parameters investigated were temperature=25-30 plus or minus C, transparency=0.45-0.57m, dissolved oxygen=3.0-10.9mg/l, pH=6.0-7.7, dissolved carbon dioxide=5.46-28.3mg/l, total alkalinity=44.37-80.0ppm, chemical oxygen demand=31.88-72.18mg/l and biological oxygen demand=0.66-48.34mg/l. Plankton composition varies and was made of four families of phytoplankton namely: Cyanophyceae, Chlorophyceae, Dinophyceae and Diatomida; and four families of zooplankton viz: Protozoa, Rotifera, Copepoda and Dinoflagellates. Farm 1 and 6 recorded the highest average weight of about 1.0kg and average total length of about 40.0cm for the two fish species. This study showed that fish yield was dependable on the quality and management of pond water characteristics

Relationship of dimensions and weight in freshwater planktonic crustaceans. [Translation from: Doklady Akademii Nauk SSSR 84(1) 153-156, 1952. ]

There is no doubt that determination of the biomass of zooplankton (primarily of crustaceans) will be taken into consideration in practice and limnological works, especially after the recent publication of fairly comprehensive tables of weights of a whole range of species of freshwater copepods and cladocerans. The usefulness of applying formulae of determining the biomass of marine crustaceans for freshwater copepods is discussed.

Taxonomic description of Peridinium lomnickii, P.lomnickii var. splendida and P. wierzejskii [Translation from: Flora Slodkowodna Polski. Tom 4. Cryptophyceae, Dinophyceae, Raphidoiphyceae, p326,328-330. Warsaw, 1974]

This partial translation from a larger paper provides taxonomic descriptions of the dinoflagellates Peridinium lomnickii, P.lomnickii var. splendida and P. wierzejskii. Illustrations are included.

The relationship between boat size and fish catches in the gillnet fishery of Lake Victoria, Uganda

The number and size composition of gillnets, fishing grounds, and the quantity and composition of fish catches were related to the size of fishing boat. The overall number of gillnets per boat increased from 20.9 + or - 2.3 nets in 5-6 m long boats to 88.6 + or - 11.8 nets in 11-12 m long boats. The proportion of large mesh sizes, + or more than 127 mm, also increased from 40% in 5-6 m long boats to 100% in boats longer than 10 m. Fish catches are related to the size of boat and this should be considered when formulating management guidelines of the lake's fishery. Promotion of large fishing boats 8 m or longer and restriction on the number and/or mesh size of gillnets of smaller boats could increase ecological and socio-economic benefits.

The relationship between aquatic macrophytes and water quality in Nta-Wogba Stream, Port Harcourt, Nigeria

An empirical survey of macrophytes distribution and biomass from four stations, along Nta-wogba stream in Port Harcourt, Nigeria, was conducted between April and December 2007, to quantify the relationship between biomass, in stream nutrients and dissolved ions. The correlation analysis indicated that the biomass of the aquatic macrophytes under consideration, Einochloa pyramidalis; Diplazum sammatii; Cyperus difformis; Alternathera sessilis and Ludwigia decurrens were significantly (P<0.05) related to the nutrients: sulphate, ammonium; nitrate, and phosphate in all the stations. The measurement of total dissolved solid, which is correlated to ionic concentrations and turbidity, provided a rough indication of in stream light availability.

Macrophyte - mollusc relationship in Lake Kariba

Five species of submerged vegetation Lagarosiphon ilicifolius, Najas pectinata, Vallisneria aethiopica, Ceratophyllum demersum and Potamogeton octandrus; 7 species of gastropods Melanoides tuberculata, Bellamya capillata, Biomphalaria pfeifferi, Bullinus tropicus, Cleopatra sp, and Lymnaea natalensis and 4 species of bivalves Corbicula africana, Caelatura mossambicensis, Mutela dubia and Aspatharia wahlbergii are correlated with environmental variables particularly slope and transparency, in Lake Kariba. A stepwise regression analysis further revealed interdependence between (Cleopatra sp., B. pfeifferi, L. natalensis, B. capillata, and V. aethiopica as well as between as between C. mossambicensis and L. ilicifolius and N. pectinata. The dependence of B. pfeifferi, L. natalensis, B. capillata, Cleopatra sp. on V. aethiopica and C. mossambicensis on L. ilicifolius and N. pectinata implies that a change in the biomass of the vegetation species may affect distribution and biomass of the faunal species.

The effects of temperature on hatching and survival of northern rock sole larvae (Lepidopsetta polyxystra)

Northern rock sole (Lepidopsetta polyxystra) is a commercially important flatfish in Alaska and was recently classified as a distinct species from southern rock sole (L. bilineata). Taxonomic and vital rate data for northern rock sole are still not fully described, notably at early egg and larval stages. In this study, we provide new taxonomic descriptions of late-stage eggs and newly hatched larvae, as well as temperature-response models of hatching (timing, duration, success), and larval size-at-hatch and posthatch survival at four temperatures (2°, 5°, 9°, and 12°C). Time-to-first-hatch, hatch cycle duration, and overall hatching success showed a negative relationship with temperature. Early hatching larvae within each temperature treatment were smaller and had larger yolk sacs, but larvae incubated at higher temperatures (9° and 12°C) had the largest yolk reserves overall. Despite having smaller yolks, size-at-hatch and the maximum size achieved during the hatching cycle was highest for larvae reared at cold temperatures (2° and 5°C), indicating that endogenous reserves are more efficiently used for growth at these temperatures. In addition, larvae reared at high temperatures died more rapidly in the absence of food despite having more yolk reserves than cold-incubated larvae. Overall, northern rock sole eggs and larvae display early life history traits consistent with coldwater adaptation for winter spawning in the North Pacific.

Relationship between abundance of juvenile rockfishes (Sebastes spp.) and environmental variables documented off northern California and potential mechanisms for the covariation

We estimated annual abundance of juvenile blue (Sebastes mystinus), yellowtail (S. f lavidus), and black (S. melanops) rockfish off northern California over 21 years and evaluated the relationship of abundance to oceanographic variables (sea level anomaly, nearshore temperature, and offshore Ekman transport). Although mean annual abundance was highly variable (0.01−181 fish/minute), trends were similar for the three species. Sea level anomaly and nearshore temperature had the strongest relationship with interannual variation in rockfish abundance, and offshore Ekman transport did not correlate with abundance. Oceanographic events occurring in February and March (i.e., during the larval stage) had the strongest relationship with juvenile abundance, which indicates that year-class strength is determined during the larval stage. Also of note, the annual abundance of juvenile yellowtail rockfish was positively correlated with year-class strength of adult yellowtail rockfish; this finding would indicate the importance of studying juvenile abundance surveys for management purposes.

The relationship between smolt and postsmolt growth for Atlantic salmon (Salmo salar) in the Gulf of St. Lawrence

The interaction of ocean climate and growth conditions during the postsmolt phase is emerging as the primary hypothesis to explain patterns of adult recruitment for individual stocks and stock complexes of Atlantic salmon (Salmo salar). Friedland et al. (1993) first reported that contrast in sea surface temperature (SST) conditions during spring appeared to be related to recruitment of the European stock complex. This hypothesis was further supported by the relationship between cohort specific patterns of recruitment for two index stocks and regional scale SST (Friedland et al., 1998). One of the index stocks, the North Esk of Scotland, was shown to have a pattern of postsmolt growth that was positively correlated with survival, indicating that growth during the postsmolt year controls survival and recruitment (Friedland et al., 2000). A similar scenario is emerging for the North American stock complex where contrast in ocean conditions during spring in the postsmolt migration corridors was associated with the recruitment pattern of the stock complex (Friedland et al., 2003a, 2003b). The accumulation of additional data on the postsmolt growth response of both stock complexes will contribute to a better understanding of the recruitment process in Atlantic salmon.

Length-weight relationship of fishes caught by trawl off Alexandria, Egypt

This paper presents the length-weight relationship parameters (a and b) for 29 fish species, belonging to 16 families, taken by otter trawl fishing from Egyptian Mediterranean waters. The b values obtained ranged from 2.50 to 3.44 (with a mean of 2.926).

Length-weight relationship of fishes from Yemen waters (Gulf of Aden and Red Sea)

The data for this study were gathered between 1993 and 1996 on board commercial trawlers from Somalia, China and Yemen and also from the research vessel Ibn Magid belonging to the Marine Science and Resources Research Centre, Aden, Republic of Yemen. Fish were identified using the FAO species identification literature. All fish were measured to the nearest mm (total length) and weighed to the nearest g. Sex was determined by dissection after the length and weight had been measured. The length-weight relationships were calculated using least-squares regression on log-transformed data and the parameters of the relationship of the form of W=aL super(b) are summarized. Maximum and minimum size of fish sampled are also given. Common names and recent changes in nomenclature were taken from ICLARM's FishBase.