Wetlands and coastal water quality: Should wetland size matter?

Generally, wetlands are thought to perform water purification functions, removing contaminants as water flows through sediment and vegetation. This paradigm was challenged when Grant et al. (2001) reported that Talbert Salt Marsh (Figure 1.) increased fecal indicator bacteria (FIB) output to coastal waters, contributing to poor coastal water quality. Like most southern California wetlands, Talbert Salt Marsh has been severely degraded. It is a small (10 ha), restored wetland, only 1/100th its original size, and located at the base of a highly urbanized watershed. Is it reasonable to expect that this or any severely altered wetland will perform the same water purification benefits as a natural wetland? To determine how a more pristine southern California coastal wetland attenuated bacterial contaminants, we investigated FIB concentrations entering and exiting Carpinteria Salt Marsh (Figure 2.), a 93 ha, moderate-sized, relatively natural wetland.(PDF contains 4 pages)

Conservation and sustainable utilization of Nigerian ornamental fishes

The paper assessed qualitatively the threat status of nigerian freshwater fishes that are presently being exported and those that have potential in aquarium trade using such criteria as rarity, size at maturity, mode of reproduction, human population density, habitat degradation, pollution and range of each species among others. For their conservation captive breeding of these fishes were proffered with information that can assist collectors, exporter and aquaculturists that wants to breed polypterids, Butterfly fish, Knife fish, Elephantfish, Pollymyrus isidori, Arnordichthys spilopterus, Nannaethiops unitaeniatus, Killifishes, Polycentropsis abbreviatta, Cichlids, Ctenpomas, Mastacembelids and Tetraodon lineatus

Comparative study on the catch efficiency and size selection of entangling nets in Lake Kainji, Nigeria

The relative catch performance and selectively of gillnets and trammel nets were investigated in 12 sampling stations in Lake Kainji, Nigeria. 3 types of nets with dimensions 50mx3m were constructed using 76mm and 178mm meshsizes for two gillnets, 76mm and 178mm meshsizes for the lint and ar mour nets of the trammelnets respectively. All the nets were randomly ganged together to form a fleet of nine nets each, and were set twice in each of the 12 stations which gave a total of 24 fishing operations. A total of 365 fish weighing 88.9kg and belonging to 16 different species were caught in all the nets. The trammelnet had the highest catch by number and weight constituting 60% and 69.22% of the total catch and weight respectively with a relative species Diversity Index of 0.82. This was followed by 76mm gillnet which constituted 38.63% by number, 28.09% by weight, 0.69 relative Species Diversity Index. The 178mm gillnet had the least catch of 1.37% and 2.9% by number and weight respectively with 0.25 relative Species Diversity Index. There was significant difference (P<0.05) in the number and weight of fish caught in the different nets. The minimum selection length for these species caught were the same for each net. The trammel net had a wider selection range that skewed to the right, a higher modal and median length indicating larger individual species being entangled in the net

The effects of brood stock size on the economy of catfish (Clarias anguillaris) fry production using the hormone induced natural breeding technique

89 ripe female brooders of the catfish, Clarias anguillaris (Body wt. Range 150g-1, 200g) were induced to spawn by hormone (Ovaprim) induced natural spawning technique over a period of 10 weeks. Matching ripe males were used for pairing the females at the ratio of two males to a female. Six ranges of brood stock body weights were considered as follows; <200g; 200g-399g; 400g-599g; 600-799g; 800g-999g; > 1000g and the number of fry produced by each female brooder was scored/recorded against the corresponding body weight range. The number of fry per unit quantity of hormone and the cost of production a fry based on the current price of Ovaprim (hormon) were determined so as to ascertain most economic size range. The best and most economic size range was between 400g-599g body weight with about 20,000 fry per ml of hormone and N0.028 per fry, while the females above 1000g gave the poorest results of 9,519 fry per ml of hormone and N0.059 per fry. For optimum production of Clarias anguillaris fry and maximum return on investment female brooders of body weights ranging between 400g-599g are recommended for hormone induced natural breeding exercises

Optimizing the benefits from Nigerian small and medium size reservoirs through cooperative management approach

The paper traces the different management practices adopted for Nigerian inland water bodies from the Colonial era to independence. It observes that the full potentials of these waters have never been realized over the years due to the absence of an effective management. The replacement of the traditional fisheries management by the centralized top-down approach by government after independence has not helped matters. Lately, the cooperative/community-based management approach has taken the centre stage worldwide. This has been identified to offer the most viable and equitable option towards the attainment of an optimum utilization of the fisheries resource. The entire community sensing security of tenure and enjoying some of the benefits from access control will actively take responsibility and enforcement. The paper drew experiences from some water bodies in Bangladesh, Philippines, Benin Republic and Malawi showing sound management strategy that, if adopted for our small and medium size reservoirs and other water bodies, would help optimize on an sustainable manner the benefits from those water bodies

The effects of brood stock size on the economy of catfish (Clarias anguillaris) fry production using the hormone induced natural breeding technique

89 ripe female brooders of the catfish, Clarias anguillaris (Body wt. Range 150g-1, 200g) were induced to spawn by hormone (Ovaprim) induced natural spawning technique over a period of 10 weeks. Matching ripe males were used for pairing the females at the ratio of two males to a female. Six ranges of brood stock body weights were considered as follows; <200g; 200g-399g; 400g-599g; 600-799g; 800g-999g; > 1000g and the number of fry produced by each female brooder was scored/recorded against the corresponding body weight range. The number of fry per unit quantity of hormone and the cost of production a fry based on the current price of Ovaprim (hormon) were determined so as to ascertain most economic size range. The best and most economic size range was between 400g-599g body weight with about 20,000 fry per ml of hormone and N0.028 per fry, while the females above 1000g gave the poorest results of 9,519 fry per ml of hormone and N0.059 per fry. For optimum production of Clarias anguillaris fry and maximum return on investment female brooders of body weights ranging between 400g-599g are recommended for hormone induced natural breeding exercises

Managing Nile perch using slot size: is it possible?

The fishery of Lake Victoria became a major commercial fishery with the introduction of Nile perch in 1950s and 1960s. Biological and population characteristics point to a fishery under intense fishing pressure attributed to increased capacity and use of illegal fishing gears. Studies conducted between 1998 to 2000 suggested capture of fish between slot size of 50 to 85 cm TL to sustain the fishery. Samples from Kenya and Uganda factories in 2008 showed that 50% and 71% of individuals processed were below the slot size respectively. This study revealed that fish below and above the slot has continued being caught and processed. This confirms that the slot size is hardly adhered to by both the fishers and the processors. The paper explores why the slot size has not been a successful tool in management of Nile perch and suggests strategies to sustain the fishery

Synopses of research on shrimps: 1. The common shrimp species of Sierra Leone's coastal waters: their distribution, abundance and size composition

The authors present quantitative information on the shrimp resources of Sierra Leone waters. Four of the nine species present have been studied, of which Paenaeus duorarum notialis is dominant in the fishery. Synoptic surveys were undertaken in June 1977, and March 1978, to determine the abundance of the shrimp stock on the inshore shelf. The temperature-salinity-depth curves for the fishing ground show the existence of three water masses. The majority of fish caught were sciaenids, with some sparids also being taken. Detailed discussion of distribution and abundance of individual species of shrimp is given. The surveys have shown that the Banana Islands are the most productive shrimp grounds in the country, and the authors believe that they can support a viable shrimp industry for several years to come at present rates of exploitation

Some observations on the temporal variations of size of copepods and some answers to questions on their biology. [Translation from: Internationale Revue der Gesamten Hydrobiologie und Hydrographie 17 99-114, 1927.]

Until now observations on the temporal variation of size of freshwater copepods have not provided much information. Other observers only mention in passing this or that phenomenon from which it is possible to deduct termporal variations. In this study Cyclops strenuus s.l., a freshwater species of fairly wide distribution, is studied in two water bodies. The author studies the systematic, placing of inhabitants described as C. strenuus Fischer in both locations, their annual life cycle, and their annual size variations.

On the methods of determining size/weight characteristics of food organisms of fish. (Determination of the length of Copepoda in larval stages by egg-laying females of the free living freshwater Copepoda). [Translation from: Voprosy Ikhtiologii 14, 182-194, 1960. ]

As is known, copepods play an important role in the nutrition of fish. Therefore with a view to facilitating research on the study of the quantitative side of feeding, there have recently appeared a considerable number of papers devoted to the development of methods for determining the wet. weight of these crustaceans. For the further facilitating of research in the nutrition of fish it would be of great interest to clarify the problem, is there not some kind of rule in the growth of the crustaceans during metamorphosis, and if there is such a rule is it not possible, to determine the length of the larvae at each stage, not by measuring them, but by using the formulae derived on the basis of these rules. This article examines the growth curves of different species of freshwater Copepoda, obtained on the basis of experimental observations in cultures or by way of measurement of mass material at all stages of development in samples from water-bodies. The authors study in particular the ratio of the mean diameter of the eggs to the mean length of the egg-bearing females.

Studies on the mouth size of fish larvae. Method and conclusions only [Translation from: Bulletin of the Japanese Society of Scientific Fisheries 36, 353-368, 1970]

This study was conducted to look into the relationship between mouth size and the total length of larval fish, and the growth in total length of larval fish in one or within a one-year period. Study material was gathered in the South China Sea, the Bay of Bangkok and the Vietnamese coast. This translation focuses on methods and conclusions of the original (longer) paper.

Ecological significance of seasonal variation in clutch-size of Arctodiaptomus bacillifer in alpine lakes of high altitudes (Val Bognanco) [Translation from: Bollettino di Zoologia 37 491-492, 1970]

This brief paper describes the significance of seasonal variation in clutch-size of the copepod Arctodiaptomus bacillifer in alpine lakes of high altitudes (Val Bognanco). Seasonal dynamics of the zooplankton of these lakes was studied during summer and autumn of 1968 and 1969and results are summarised.

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.

Socio-economic implications of the fish export trade on the fishers and fisheries of Lake Victoria in Uganda

The purpose of this study was to investigate the implications of the fish export trade on the fishers and the fisheries resources of Lake Victoria, Uganda with respect to sustainability. Eight fish processing factories and ninety fishers were qualitatively investigated. Socio-economic characteristics of fishers and the economic characteristics of fish factories formed a basis for the analysis. Results of the research indicate that there is a relationship between the growth in fish export trade, particularly the growth in industrial fish processing (for export) and declining fisheries resources of the lake. However, whether or not that impact is positive or negative, and to what extent there is an impact, is highly dependent upon the underlying socio-economic considerations of the fishers to the process. The fish-ban imposed by the European Union countries was particularly decried by fishers and factory owners as the main cause for the present poverty among the fishers. Fundamentally, several conflicting issues: ecological, physical and economic activities are a threat to the sustainability of the Lake Victoria fisheries, and for all that depend on and interact with the lake. There is urgent need to address the immediate issue of the growing riparian population and the global fish trade, to educate and train all the relevant actors in appropriate fisheries management techniques. Attitudes of fishers towards the fish factory developments are positive and this is a way forward for co-management for the sustainability of the fisheries resource.

Size composition of the catches of the pink shrimp Penaeus duorarum notialis in the shrimp fishery of Sierra Leone

Measurements were taken of size distribution of P. d. notialis collected off Sierra Leone over a period of six months from October 1977 to March 1978. From the frequency distribution curves it is observed that the curves for male shrimps show only one or two major modes, which show prominence between 12.5 and 14.1 cm of total length. Females mostly exhibited size groups with three or four different length ranges and occasional occurrence of 1 to 5 modes. These size groups were observed to show continuous changes. No one group could be said to be permanent. The point of entry into the fishery of male shrimps was found to be at an average total length of 10.5 cm, while females did so at 11 cm. Sex ratios in the different samples were usually 1:1 but in one case the males were more numerous by 2:1 and in four other samples females were significantly preponderent. These departures from the 1:1 ratio may have been artificially created by sorting of the catches on board the ships.