Mortality estimates of the four major Cichlid fishes of Umuoseriche Lake, Imo State, Nigeria

The mortality of the four major cichlid fishes of Urnuoseriche Lake is the subject of this paper. Mortality I as estimated by five techniques, vary amongst the cichlid fishes, viz, Tilapia carbrae, Tilapia mariac, Tilapia zilli cend (hrornoditilapfa guntheri. The highest mortality rate was recorded for T mariac where the total mortality (Z) was 2.06; and natural mortality (M) was 1.8949. This species was also the most highly exploited species of fish with an exploitation ratio of0.566 (56.6%) and exploitation rate of 0.494. The least exploited cichlid fish is (. gun/hen where an exploitation ratio of 0.43209%) and exploitation rate of 0.2225 was recorded. In C'. guntheni, total mortality was 0.726 and natural mortality was 0.413 1. In T zilli, total mortality was 1.0547 wile exploitation ratio was 0.3674 (3 6.74%) and an exploitation rate was 0.2394. In T cahrae. total mortality was 1.8662: exploitation ratio was 0.4786 with an exploitation rate of 0.4045. (7 page document)

Modelling of the Subarctic North Pacific Circulation (Report of Working Group 7)

This review focuses on modelling ocean circulation and its variability in the subarctic North Pacific; it addresses issues specific to that region, and not the subject of ocean modelling in general. The performance of existing models is assessed in relation to observations in the upper ocean, intermediate waters and deep/abyssal waters. (PDF contains 87 pages)

An examination of the Community Fisheries Sub-Decree in Cambodia: changes and developments during the drafting process

This study examines the development of the Community Fisheries Sub-Decree. From its promulgation in late 2000 through its draft form in June 20021, this sub-decree has gone through over 25 drafts. Initially, the writing process involved the public intimately: community meetings were conducted, NGOs contributed their knowledge and expertise, and then, with these consultations in mind, the newly-formed Community Fisheries Development Office (CFDO) in the Department of Fisheries (DoF) drafted the sub-decree. Over the following year and a half, the sub-decree went through numerous changes, some of which fundamentally alter the tenor of the legislation. This includes the deletion of some of the primary issues of rural communities, such as what fishing gears they can use and whether they can participate in patrolling the fishing area. While the final form is still pending, there are many questions as to the positive effects that the sub-decree will ultimately have on people’s livelihoods when it is finally approved. This research was undertaken to track the development of the sub-decree to gain a better understanding of how the Cambodian policy-making system functions. Consultations were undertaken with the DoF and CFDO before the research began, both of which agreed to the study. It is hoped that this report will help not only those interested in community fisheries issues, but also those who want to advocate on other Cambodian development issues as well. Due to the sensitive nature of the subject material, and the fact that the sub-decree is still pending, the author has conducted interviews with the express purpose of keeping them confidential. Therefore, no individual will be quoted directly in this study. In addition, many of the English versions of the drafts examined were unofficial translations. The author has made no effort to correct the English in the drafts. Moreover, there are also questions regarding the drafts and their sequence, as no government records were kept of the process or the changes that were made along the way. These have been compiled after the fact. (33 p.)

Fishery resources of the United States of America

The term “fishery resources” is used in this book with a broad application. It includes the populations of the fishes and other organisms useful to men, the environment that makes life possible for them, the industry that exploits and utilizes them, and our knowledge about them by which we can conserve their productivity. This book aims to survey the present status of all these aspects of those fishery resources that are used or are available for use by United States anglers and commercial fishermen. It is planned primarily for the Congress, at its request, with the idea of giving to busy people, in condensed fashion, a perspective on its subject. (pdf contains 142 pages)

Tunas and tuna fisheries of the World: an annotated bibliography, 1930-1953

This bibliography attempts to list, with descriptive annotations and a subject index, important literature published between 1930 and 1953 dealing with the tunas and their fisheries in all parts of the world. It is thus a continuation of Corwin's (1930) work, which extended with similar scope through 1929, and an extension of Shimada's (1951), which was limited to the biology of Pacific tunas. The tunas with which it deals are those fishes customarily so-called in commercial parlance and usually classified in the genera Thunnus, Neothunnus, Parathunnus, Germo, Katsuwonus, Euthynnus and Auxis and their various synonyms. All aspects of the biology of the tunas are dealt with, as are descriptions and histories of all types of tuna fisheries, commercial and exploratory tuna fishing methods and results, fishing gear, catch statistics, and fishery management, but processing technology, economics and marketing, folklore, and purely literary references have been excluded.

Proceedings of the International Workshop on age determination of oceanic pelagic fishes: Tunas, billfishes, and sharks, Miami, Florida, February 15-18,1982

Accurate and precise estimates of age and growth rates are essential parameters in understanding the population dynamics of fishes. Some of the more sophisticated stock assessment models, such as virtual population analysis, require age and growth information to partition catch data by age. Stock assessment efforts by regulatory agencies are usually directed at specific fisheries which are being heavily exploited and are suspected of being overfished. Interest in stock assessment of some of the oceanic pelagic fishes (tunas, billfishes, and sharks) has developed only over the last decade, during which exploitation has increased steadily in response to increases in worldwide demand for these resources. Traditionally, estimating the age of fishes has been done by enumerating growth bands on skeletal hardparts, through length frequency analysis, tag and recapture studies, and raising fish in enclosures. However, problems related to determining the age of some of the oceanic pelagic fishes are unique compared with other species. For example, sampling is difficult for these large, highly mobile fishes because of their size, extensive distributions throughout the world's oceans, and for some, such as the marlins, infrequent catches. In addition, movements of oceanic pelagic fishes often transect temperate as well as tropical oceans, making interpretation of growth bands on skeletal hardparts more difficult than with more sedentary temperate species. Many oceanic pelagics are also long-lived, attaining ages in excess of 30 yr, and more often than not, their life cycles do not lend themselves easily to artificial propagation and culture. These factors contribute to the difficulty of determining ages and are generally characteristic of this group-the tunas, billfishes, and sharks. Accordingly, the rapidly growing international concern in managing oceanic pelagic fishes, as well as unique difficulties in ageing these species, prompted us to hold this workshop. Our two major objectives for this workshop are to: I) Encourage the interchange of ideas on this subject, and 2) establish the "state of the art." A total of 65 scientists from 10 states in the continental United States and Hawaii, three provinces in Canada, France, Republic of Senegal, Spain, Mexico, Ivory Coast, and New South Wales (Australia) attended the workshop held at the Southeast Fisheries Center, Miami, Fla., 15-18 February 1982. Our first objective, encouraging the interchange of ideas, is well illustrated in the summaries of the Round Table Discussions and in the Glossary, which defines terms used in this volume. The majority of the workshop participants agreed that the lack of validation of age estimates and the means to accomplish the same are serious problems preventing advancements in assessing the age and growth of fishes, particularly oceanic pelagics. The alternatives relating to the validation problem were exhaustively reviewed during the Round Table Discussions and are a major highlight of this workshop. How well we accomplished our second objective, to establish the "state of the art" on age determination of oceanic pelagic fishes, will probably best be judged on the basis of these proceedings and whether future research efforts are directed at the problem areas we have identified. In order to produce high-quality papers, workshop participants served as referees for the manuscripts published in this volume. Several papers given orally at the workshop, and included in these proceedings, were summarized from full-length manuscripts, which have been submitted to or published in other scientific outlets-these papers are designated as SUMMARY PAPERS. In addition, the SUMMARY PAPER designation was also assigned to workshop papers that represented very preliminary or initial stages of research, cursory progress reports, papers that were data shy, or provide only brief reviews on general topics. Bilingual abstracts were included for all papers that required translation. We gratefully acknowledge the support of everyone involved in this workshop. Funding was provided by the Southeast Fisheries Center, and Jack C. Javech did the scientific illustrations appearing on the cover, between major sections, and in the Glossary. (PDF file contains 228 pages.)

A comparative assessment of the methods of control of water hyacinth infestation with regards to fish production

Water hyacinth (Eichhornia crassipes) has been subject of three control methods since its arrival into the Nigerian freshwater lagoon system in 1984 - mechanical, chemical and biological. An assessment of these three methods seems to suggest that mechanical and chemical control methods, both of which being costly, must be applied either solely or integrated to combat the present level of considerable infestation in Nigeria. The biological control methods are advisable for slow, sustained control and can only cope with low levels of infestation. It is thus concluded that the preliminary control method should be mechanical or chemical to effectively abate the nuisance plant, followed by biological control once infestation levels have been sufficiently reduced

The macroinvertebrate fauna of pools in the floodplain (fadama) of the Anambra River, Nigeria

The Anambra River is the largest tributary of the lower Niger River below Lukoja. Between the months of May and November the river is subject to seasonal flooding from heavy precipitation and land runoff into the drainage system. During the flood phase, pools form on the floodplains (known as the fadama) and these pools receive materials and biota from the main river channel. The biota often includes representatives of freshwater vertebrates (including fishes) and invertebrates. On this brief note, the authors report on the macroinvertebrates found during preliminary studies on four fadama pools during the non-flood season between December 1994 and April 1995. 523 specimens were collected, of which 86% were arthropods, 9% were annelids (mostly Tubifex and Nais) and a few leeches (Hirudo), and 5% were gastropod molluscs of the arthropods, 75% were insects particularly Hemiptera and Diptera.

The role of ciliates in the pelagic life cycle of the Mediterranean [Translation from: Rapports et Proces Verbaux des Reunions-Conseil International pour l'Exploration de la Mer 17, 511-512, 1963]

During hydrographic and plankton studies carried out since 1960 in the coastal zone between the Ebro and Castellon (western Mediterranean), data has been collected which confirms the importance of ciliates in the composition and activity of the plankton. The ciliates in 413 samples of 100 ml of water were counted, having been examined with the Utermohl microscope after sedimentation. The samples studied were distributed according to the density of their population. subject for study. The author concludes that recognition of the role of ciliates as an important link in the food chain of the sea would simplify the interpretation of certain problems posed by the nutrition of certain groups of planktonic animals.

Aspects of the washout of salmonid eggs. 4. Effects of a standard mechanical shock, applied at different stage of development, upon survival and development of eggs of brown trout (Salmo trutta L.)

It is generally accepted by fish culturists that salmonid eggs are sensitive to mechanical shock and that the sensitivity varies with the stage of development of the eggs. In general, the period of greatest sensitivity is thought to occur between fertilization and ”eyeing”. However, it is reasonable to expect that, during a period (perhaps of several hours) following fertilization, sensitivity will be low because in nature during this period the eggs may be subject to some mechanical shock caused by the parent fish covering them with gravel. In 1983-4 and 1984-5 experiments were performed on brown trout (Salmo trutta L.) eggs to examine the effect of a standard mechanical shock (c. 2,500 eggs in 1983-4 and c. 8,400 eggs in 1984-5) at various stages of development upon survival to hatching and time of hatching.The results of these experiments are reported in this study.

A tool for better management of water quality during periods of algal blooms: the case of the River Oise

Like other rivers in the Paris area, the Oise is subject to important seasonal algal blooms. This eutrophication generates notable problems for the production of drinking-water from a treatment plant on the river at Méry. A mathematical model has been developed to simulate variation in water quality in a pre-treatment storage basin, and another model is currently being adapted to model the River Oise. Integration of the two models should provide a comprehensive tool for predicting variations of phytoplankton and water-quality parameters associated with algal blooms. This will be a decision-aid for optimizing control of the treatment process for providing potable water.

The microbiological quality of water: the nature of the problem

Improvements in methods for the detection and enumeration of microbes in water, particularly the application of techniques of molecular biology, have highlighted shortcomings in the ”standard methods” for assessing water quality. Higher expectations from the consumer and increased publicity associated with pollution incidents can lead to an uncoupling of the cycle which links methodological development with standard-setting and legislation. The new methodology has also highlighted problems within the water cycle, related to the introduction, growth and metabolism of microbes. A greater understanding of the true diversity of the microbial community and the ability to transmit genetic information within aquatic systems ensures that the subject of this symposium and volume provides an ideal forum to discuss the problems encountered by both researcher and practitioner.

Report on the 1995 stock assessment of the Douglas catchment

The River Douglas has a long industrial heritage beginning in the early 18th century with its use by boats carrying goods between Wigan and Tarleton. The River and its tributaries have also historically been, and to a certain extent are still, subject to polluting inputs from the urban, agricultural and industrialised areas located within its catchment. During the early stages in the production of the River Douglas Catchment Management Plan, it became apparent that very little data existed on the populations of coarse and salmonid fish species within the River Douglas system. The data that did exist was largely anecdotal, consisting of catch reports from anglers or water bailiffs, or of dead and distressed fish following pollution incidents. This study was initiated to assess the status of coarse and salmonid fish species within the River Douglas system and so address the lack of knowledge. Eighty two sites were surveyed by electric fishing, including 14 sites using an electric fishing punt and up to four anodes. The data was analysed according to a new National Fisheries Classification Scheme. This classified the sites by the fish stock s present and compared the results with a database containing information from sites around the country that have similar habitat types. A stocking experiment was also undertaken in the River Lostock using chub reared at the Leyland Hatchery. These were marked with an identifiable blue spot in the spring of 1995 and then released into three, previously surveyed, locations in the river. These sites were then resurveyed during the summer stock assessment. This report also Site Reports with details on monitored sites, habitat features and fishery classification.

Distribution and Apparent Abundance of the Basking Shark, Cetorhinus maximus, off the Central and Southern California Coast, 1962-85

Basking sharks, Cetorhinus maximus, are frequently observed along the central and northwestern southern California coast during the winter and spring months. These large plankton feeding elasmobranchs, second in size only to the whale shark, Rhineodon typus, had been the subject of a small commercial fishery off California in the late 1940's and early 1950's for their liver oil, rich in vitamin A, and in later years for reduction into fish meal and oil (Roedel and Ripley, 1950). These fisheries were sporadic and did not take basking sharks in large numbers.

Modeling the Potential Spread of the Recently Identified Non-Native Panther Grouper (Chromileptes altivelis)in the Atlantic Using a Cellular Automaton Approach

The Indo-pacific panther grouper (Chromileptes altiveli) is a predatory fish species and popular imported aquarium fish in the United States which has been recently documented residing in western Atlantic waters. To date, the most successful marine invasive species in the Atlantic is the lionfish (Pterois volitans/miles), which, as for the panther grouper, is assumed to have been introduced to the wild through aquarium releases. However, unlike lionfish, the panther grouper is not yet thought to have an established breeding population in the Atlantic. Using a proven modeling technique developed to track the lionfish invasion, presented is the first known estimation of the potential spread of panther grouper in the Atlantic. The employed cellular automaton-based computer model examines the life history of the subject species including fecundity, mortality, and reproductive potential and combines this with habitat preferences and physical oceanic parameters to forecast the distribution and periodicity of spread of this potential new invasive species. Simulations were examined for origination points within one degree of capture locations of panther grouper from the United States Geological Survey Nonindigenous Aquatic Species Database to eliminate introduction location bias, and two detailed case studies were scrutinized. The model indicates three primary locations where settlement is likely given the inputs and limits of the model; Jupiter Florida/Vero Beach, the Cape Hatteras Tropical Limit/Myrtle Beach South Carolina, and Florida Keys/Ten Thousand Islands locations. Of these locations, Jupiter Florida/Vero Beach has the highest settlement rate in the model and is indicated as the area in which the panther grouper is most likely to become established. This insight is valuable if attempts are to be made to halt this potential marine invasive species