Fisheries statistical bulletin, Kainji Lake, Nigeria, 1998

A tabulated summary is presented of the main fisheries data collected to date (1998) by the Nigerian-German Kainji Lake Fisheries Promotion Project, together with a current overview of the fishery. The data are given under the following sections: 1) Fishing localities and types; 2) Frame survey data; 3) Number of licensed fishermen by state; 4) Mesh size distribution; 5) Fishing net characteristics; 6) Fish yield; 7) Total annual fishing effort by gear type; 8) Total annual value of fish landed by gear type; 9) Graphs of effort and CPUE by gear type. (PDF contains 36 pages)

Predictions of fish yields and the status of the Kainji Lake fishery, 1998

Length frequency data was collected for the 6 main species from the Kainji Lake fishery for up to 16 months. Growth parameters were estimated and used for virtual - population and length based cohort analysis. The results from cohort analysis suggest that before the ban on beach seines the maximum economic yield from the fishery was overshot by 70%. Yield per recruit analysis showed that the fish are caught far below their optimum size. Fishing gears and the timing responsible for this early mortality have been identified. After the eradication of seines from the lake a 10% increase in total catch revenue can be expected from the fishery. This is equivalent to an increase in income of Naira 18,300 per annum for each fishing entrepreneur using other methods. A scenario for the regulation of cast net mesh size together with the ban of beach seines has been presented. A further increase of Naira 142 million (N25,500 per entrepreneur) can be anticipated if this is implemented by the Kainji Lake Fisheries Management and Conservation Unit. It is expected that the annual increase in fishing effort presently experienced will cause future yields to decline. The rate of the decline has been reduced by the eradication of the beach seine fishery and will further fall if the minimum mesh size for cast nets is implemented. A recommendation is made to the Kainji Lake Fisheries Management and Conservation Unit to first consolidate the beach seine ban and then to implement a ban of undersized cast nets. (PDF contains 70 pages)

Fisheries statistical bulletin, Kainji Lake, Nigeria, 1999

A tabulated summary is presented of the main Lake Kainji fisheries data collected to date (1999) by the Nigerian-German Kainji Lake Fisheries Promotion Project, together with a current overview of the fishery. The data are given under the following sections: 1) Fishing localities and types; 2) Frame survey data; 3) Number of licensed fishermen by state; 4) Mesh size distribution; 5) Fishing net characteristics; 6) Fish yield; 7) Average monthly CPUE by gear type; 8)Average monthly fishing activity by gear type; 9) Total annual fishing effort by gear type; 10) Total annual value of fish landed by gear type; 11) Trends of the total yield by gear type. (PDF contains 34 pages)

Selection of efficient hanging ratios of gillnet on fish catch in Lake Kainji, as means of alleviating poverty among artisanal fishermen in Nigeria

Five experimental gillnet each measuring 50mx 3m nylon multi filament netting of 3" by210/2 mesh size were constructed using 40%, 45%, 50%, 55% and 60% hanging percentages, the report was carried out at Yunawa fishing village on the eastern bank of Lake Kainji. The nets were set over night (6 hours approximately). Between April-July 2004, the fish caught by the five nets were recorded taking into consideration the three mode of capture i.e. enmeshing entanglement and wedging Weight number and percentage mean weight and number based on species at five different hanging ratios were analyzed in general 50% hanging ratio was found to be the best followed by 40% among others. There was significant difference (P<0.05) in the mode of capture for both hanging ratios. Most of the fish were caught by entanglement i.e. about 83% of the catch was by entanglement while 505 hanging ratio was the best considered after the report. The occurrence of species of the five hanging ratios has significant difference (P<0.05) in terms of catch by weight and number

Assessment of inland waters fisheries in Nigeria with implications for improved freshwater fish production, poverty alleviation and food security

Rapid Appraisals of the current fisheries situations of some selected inland water bodies in Nigeria were carried out within the framework of Aquaculture and Inland Fisheries Project (AIFP) Annex II of the National Special Programme for Food Security (NSPFS). This paper presents the results of the fishery assessment of one of the selected inland water bodies (Sabke Lake) in Nigeria with a view to optimizing the fish yield through the adoption of improved culture based fishery techniques and community-based fisheries management. The lake is unmanaged and the fishing pressure was found to be very high. Also a number of fishermen were found using small mesh size nets to crop the juveniles of highly valued fish species for an optimum catch. About 14 fishermen ought to have been engaged in full time fishing activities if the fisheries of this lake is to be managed on a sustainable basis. However, a surplus of over 100 fishermen was recorded actively fishing during the period of the study. The results further revealed that Fisheries Rules and Regulations were not established for the national exploitation and proper management of the fisheries of many inland water bodies including Sabke Lake. All these have a depilatory effect on the abundance and sizes of fish harvested from the nigerian inland water bodies especially Sabke Lake. A community based management system that establishes a participatory involvement of fishermen in the conservation and national exploitation of fisheries resources for their own well being is recommended for Sabke Lake and other inland water bodies in Nigeria

Evaluation of a new fishing pot trap (Lege) in River Rima, north western Nigeria

Based on the findings and diagnostic survey, a new fishing trap, christened Lege trap was designed and fabricated, and the performance evaluated. The 8-valve Lege trap was assessed concurrently with Malian and Ndurutu traps by the fishermen in the study area. The experiment was conducted in a randomized complete block design with one factor each replicated three times. Data collected on fish diversity number, biomass and size were subjected to descriptive statistics and analysis of variance. The results showed that 22 fish species belonging to thirteen families were caught. The prototype (Lege) trap recorded higher species diversity index (0.90) than the Malian (0.50) and Ndurutu (0.50) traps. The Lege trap also accounted for the largest number (55%) and biomass (63%) of fish caught which was significantly (P<0.05) higher than those of the Malian and Nduutu traps were. The mean length (15.03~c5.70cm), weight (60.43~c48.61g) and girth (4.77~c1.65cm) of fishes caught in the Lege trap were also significantly (P0.05) higher than those caught in the other two traps. These results demonstrated better performance of the new trap than the two conventional traps, even though the sizes of some of the fish species caught in all the traps were below those allowed by the Sokoto State Fisheries Edict where the study was conducted. Therefore, since it is desirable to develop conservation-oriented trap at a least cost, it is necessary to research further on the number of valves and mesh size of the new trap

Influence of number of valves on catch composition of a fishing pot trap (Lege) in River Rima, north western Nigeria

Three types of prototype (Lege) traps with different numbers of entrance valves were evaluated in River Rima, north western Nigeria. The traps contained 4,6 and 8 valves, tagged 4-V, 6-V and 8-V respectively. The experiment was carried out in a randomized complete block design with one factor each replicated three times. Data collected on fish diversity, number biomass and sizes were subjected to descriptive statistics and analysis of variance. The results of the catch composition showed close diversity index of 0.86 for 6-V, 0.80 for 8-V and 0.60 for 4-V Lege traps. However, the number (41%) and biomass 48%) of fish caught in the 6-V Lege trap were significantly (P0.05) higher than those caught in the other traps. There was no definite trend in the sizes (length and girth) of fish caught in the traps. On the basis of species diversity, and the number and biomass of fish caught, the 6-V Lege showed preference for adoption than the other two traps. However, further studies are recommended on the appropriate mesh size net for the trap in line with the provisions of fisheries edicts

Study on the effects of three fishing baits on the catch composition of malian traps in Lake Kainji

The studies on the effects of three fishing baits on the catch composition of Malian traps in Lake Kainji were investigated. The traps were set between Monai and Taafa fishing villages in the Southern basin of the lake, baited with their respective treatment and were inspected daily for twelve days. A total of 218 fish were caught, of which the highest (54.59%) was caught by corn bran, while the lowest (11.01%) was caught by stomach content and rice bran caught 34.4%. The fish caught comprised of 15 species belonging to 8 families. There was no significant different (P>0.05) in the catch of the various baits. The weight also followed the same trend as the number of fish caught. However, both baits showed better efficiency for Alestes baremose. Tilapia zilli, S. galilaeus, Oreochromis niloticus, Labeo coubie and Distichodus rostratus than other species caught. There was a wide range between the inimum and maximum size of species caught, which showed the efficiency of the traps in capturing small size, juveniles and the adult of large fish species due to small mesh size (1") net-cover of the trap. Recommendations were made on the use of corn and rice bran as baits enhancing catch efficiency for fishes such as O.niloticus, T. zilli, T. galilaeus and D. rostratus

Responsible fisheries enhancing poverty alleviation of fishing communities of Lake Kainji

The attributes of responsible fisheries in enhancing Poverty Alleviation of fishing Communities of Lake Kainji were appraised. After impoundment in 1968, the catch per unit effort of fish continued on a downward trend, which suggested a decline in the fish population as a result of improper fishing methods such as the use of small mesh size nets, fish poisoning, destructive fishing gears like beach seine nets. The Nigerian-German (GTZ) Kainji Lake Fisheries Promotion Project intervention brought an increase in yields for the lake in 1996. The estimated annual yield was put at 38.244 metric tones in 1996, an increase of 18 % from the yield recorded in 1995 due to improvement in fishing and conservation methods. The result of catch assessment study carried out in 2003 as a follow up to GTZ intervention is presented. This reveals 15 family and 40 species of fish recorded. Which shows that Lake Kainji still has very high diversity and abundance of fish species. The paper suggests ways to encourage fishing communities to adopt new innovation or strategies by the government and non-governmental organization, which will go a long way in alleviation poverty among the fisher folks

Influence of number of valves on catch composition of a fishing pot trap (Lege) in River Rima, north western Nigeria

Three types of prototype (Lege) traps with different numbers of entrance valves were evaluated in River Rima, north western Nigeria. The traps contained 4,6 and 8 valves, tagged 4-V, 6-V and 8-V respectively. The experiment was carried out in a randomized complete block design with one factor each replicated three times. Data collected on fish diversity, number, biomass and sizes were subjected to descriptive statistics and analysis of variance. The results of the catch composition showed close diversity index of 0.86 for 6-V, 0.80 for 8-V and 0.60 for 4-V Lege traps. However, the number (41%) and biomass (48%) of fish caught in the 6-V Lege trap were significantly (P<0.05) higher than those caught in the other traps. There was no definite trend in the sizes (length and girth) of fish caught in the traps. On the basis of species diversity, and the number and biomass of fish caught, the 6-V Lege showed preference for adoption than the other two traps. However, further studies are recommended on the appropriate mesh size net for the trap in line with the provisions of fisheries edicts

Feeding selectivity of brown trout (Salmo trutta) in Loch Ness, Scotland

The aim of this study was to compare statistically the zooplankton assemblage ingested by brown trout (Salmo trutta) in Loch Ness with that of the zooplankton in the water column. This would allow the examination of the apparent paradox that very few copepods appear to be consumed by trout at a time of year when they are numerous and readily available as food. The investigation was limited to the crustacean zooplankters, since the Rotifera are generally so small that they are only of interest to fish in the first few days of life. 25 trout were obtained from anglers, and the stomach contents of non-"ferox" animals analysed. Samples of pelagic zooplankton were obtained approximately monthly from 30-m vertical net-hauls (mesh size 100 km). It is concluded that the variation in dietary composition with trout wet weight indicates an ontogenetic habitat shift producing spatial separation of young and older individuals.

Selectivity of gillnets for Nile perch, Lates niloticus (L.), in Lake Victoria, Kenya

Four fleets of hanging coefficients 0.2, 0.4, 0.6 and 0.8 were used to determine size selectivity and selection factors of Nile perch populations. There was a linear relationship between mesh size and modal length of capture. Positively skewed length frequency distributions were found for smaller mesh sizes with entanglement becoming more prominent in mesh sizes above 101 mm. Nets of 114 to 141 mm stretched mesh yielded higher economic returns than small meshes, the catch consisting of few largefish.

Zooplankton - fish interaction in the littoral zone of Nyanza Gulf, Lake Victoria

The zooplankton community of the littoral zone of Nyanza Gulf, Lake Victoria, was studied between June 1998 and June 1999 to identify and quantify various zooplankton groups, and investigate the interactions that occur between them and the littoral fish through the food chain. Zooplankton samples were collected from five stations using a 83 micro-m mesh size plankton net hauled vertically through the water column. Fish samples were obtained by beach seine, except at Gingra (May 1999), where trawl samples were used. Gut/stomach analysis was carried out on the three major commercial species, Lates niloticus (L.), Oreochromis niloticus (L.) and Rastrineobola argentea (Pellegrin).

I. Quantum mechanics of one-dimensional two-particle models. II. A quantum mechanical treatment of inelastic collisions

Part I

Solutions of Schrödinger’s equation for system of two particles bound in various stationary one-dimensional potential wells and repelling each other with a Coulomb force are obtained by the method of finite differences. The general properties of such systems are worked out in detail for the case of two electrons in an infinite square well. For small well widths (1-10 a.u.) the energy levels lie above those of the noninteresting particle model by as much as a factor of 4, although excitation energies are only half again as great. The analytical form of the solutions is obtained and it is shown that every eigenstate is doubly degenerate due to the “pathological” nature of the one-dimensional Coulomb potential. This degeneracy is verified numerically by the finite-difference method. The properties of the square-well system are compared with those of the free-electron and hard-sphere models; perturbation and variational treatments are also carried out using the hard-sphere Hamiltonian as a zeroth-order approximation. The lowest several finite-difference eigenvalues converge from below with decreasing mesh size to energies below those of the “best” linear variational function consisting of hard-sphere eigenfunctions. The finite-difference solutions in general yield expectation values and matrix elements as accurate as those obtained using the “best” variational function.

The system of two electrons in a parabolic well is also treated by finite differences. In this system it is possible to separate the center-of-mass motion and hence to effect a considerable numerical simplification. It is shown that the pathological one-dimensional Coulomb potential gives rise to doubly degenerate eigenstates for the parabolic well in exactly the same manner as for the infinite square well.

Part II

A general method of treating inelastic collisions quantum mechanically is developed and applied to several one-dimensional models. The formalism is first developed for nonreactive “vibrational” excitations of a bound system by an incident free particle. It is then extended to treat simple exchange reactions of the form A + BC →AB + C. The method consists essentially of finding a set of linearly independent solutions of the Schrödinger equation such that each solution of the set satisfies a distinct, yet arbitrary boundary condition specified in the asymptotic region. These linearly independent solutions are then combined to form a total scattering wavefunction having the correct asymptotic form. The method of finite differences is used to determine the linearly independent functions.

The theory is applied to the impulsive collision of a free particle with a particle bound in (1) an infinite square well and (2) a parabolic well. Calculated transition probabilities agree well with previously obtained values.

Several models for the exchange reaction involving three identical particles are also treated: (1) infinite-square-well potential surface, in which all three particles interact as hard spheres and each two-particle subsystem (i.e. BC and AB) is bound by an attractive infinite-square-well potential; (2) truncated parabolic potential surface, in which the two-particle subsystems are bound by a harmonic oscillator potential which becomes infinite for interparticle separations greater than a certain value; (3) parabolic (untruncated) surface. Although there are no published values with which to compare our reaction probabilities, several independent checks on internal consistency indicate that the results are reliable.

Wirtschaftlichere Befischung des Patagonienhechtes wünschenswert?

Dueto the results of 2 exploratory cruises of R.V. "Walther herwig" and the findings of the M.S. "Weser" the hake population on the Patagonian shelf is estimated to be about 3 mill. ts. The maximum sustainable yield could be 1 mill. ts. From the population - dynamical point of view at the moment there is a need to increase the catches for the benefit of the whole stock. On the other hand it is necessary to use a minimum mesh size of 120 mm, for economical reasons too, based on selection-experiments, which were also found to be the most optimal for the SE-Atlantic hake. Remarks on distribution, age - length relationship are made.