The genesis and achievement of a limnologist: George Evelyn Hutchinson, 1903-1991

An obituary of the limnologist G.E. Hutchinson is given.

The effect of sublethal concentration of DimilinR (TH6040) on the larval development of the mud-crab Rhithropanopeus harrisii (Gould)

Sublethal DimilinR (insecticide) concentration significantly decreased the percentage survival of larval R. harrisii . This decrease was marked at low salinities, when it may have become toxic. This was true for both 25 and 30 C. Duration of larval development did not seem to be affected by sublethal DimilinR concentrations even in extremely low or high salinities. High temperature, however, shortened the time of development. No anatomical abnormality was observed. These findings are only tentative as more replicates of the experiments are needed before definite conclusions can be reached. It will be desirable to work with more salinity-temperature combinations to get a complete picture of sublethal effects under different environmental conditions.

Caribbean corals in crisis: record thermal stress, bleaching, and mortality in 2005

Background: The rising temperature of the world’s oceans has become a major threat to coral reefs globally as the severity and frequency of mass coral bleaching and mortality events increase. In 2005, high ocean temperatures in the tropical Atlantic and Caribbean resulted in the most severe bleaching event ever recorded in the basin. Methodology/Principal Findings: Satellite-based tools provided warnings for coral reef managers and scientists, guiding both the timing and location of researchers’ field observations as anomalously warm conditions developed and spread across the greater Caribbean region from June to October 2005. Field surveys of bleaching and mortality exceeded prior efforts in detail and extent, and provided a new standard for documenting the effects of bleaching and for testing nowcast and forecast products. Collaborators from 22 countries undertook the most comprehensive documentation of basin-scale bleaching to date and found that over 80% of corals bleached and over 40% died at many sites. The most severe bleaching coincided with waters nearest a western Atlantic warm pool that was centered off the northern end of the Lesser Antilles. Conclusions/Significance: Thermal stress during the 2005 event exceeded any observed from the Caribbean in the prior 20 years, and regionally-averaged temperatures were the warmest in over 150 years. Comparison of satellite data against field surveys demonstrated a significant predictive relationship between accumulated heat stress (measured using NOAA Coral Reef Watch’s Degree Heating Weeks) and bleaching intensity. This severe, widespread bleaching and mortality will undoubtedly have long-term consequences for reef ecosystems and suggests a troubled future for tropical marine ecosystems under a warming climate

Seasonal growth of King George whiting (Sillaginodes punctata) estimated from length-at-age samples of the legal-size harvest

Samples of 11,000 King George whiting (Sillaginodes punctata) from the South Australian commercial and recreational catch, supplemented by research samples, were aged from otoliths. Samples were analyzed from three coastal regions and by sex. Most sampling was undertaken at fish processing plants, from which only fish longer than the legal minimum length were obtained. A left-truncated normal distribution of lengths at monthly age was therefore employed as model likelihood. Mean length-at-monthly-age was described by a generalized von Bertalanffy formula with sinusoidal seasonality. Likelihood standard deviation was modeled to vary allometrically with mean length. A range of related formulas (with 6 to 8 parameters) for seasonal mean length at age were compared. In addition to likelihood ratio tests of relative fit, model selection criteria were a minimum occurrence of high uncertainties (>20% SE), of high correlations (>0.9, >0.95, and >0.99) and of parameter estimates at their biological limits, and we sought a model with a minimum number of parameters. A generalized von Bertalanffy formula with t0 fixed at 0 was chosen. The truncated likelihood alleviated the overestimation bias of mean length at age that would otherwise accrue from catch samples being restricted to legal sizes.

Sex ratios of Metapenaeus kutchensis George, George and Rao, 1963 and Parapenaeopsis sculptilis (Heller, 1862) in the Gulf of Kachchh, Western India

Sex ratio data of two species of penaeid prawns Metapenaues kutchensis George, George and Rao, 1963 and Parapenaeopsis sculptilis (Heller, 1862), occurring in the Gulf of Kachchh, were statistically analysed. A preponderance of females was observed in both the species and the ratio of male to female for both years combined for M. kutchensis and P. sculptilis was found to be 1:15 and 1:2.7, respectively. Chi-square analysis revealed significant difference in the sex ratio of the two species.

Technical report of frame and catch assessment surveys of Lakes Edward and George; and the Kazinga Channel conducted in January and July 2011- 2013

This study aimed at evaluating the production levels in terms of catch estimates of the artisanal fisheries of the Edward-George system in addition to providing information on the facilities and services at landing sites and the composition, magnitude and distribution of fishing effort to guide development and management of the fisheries resources of the Edward and George lakes and Kazinga channel. Specifically, the study was expected to come up with the following outputs:- a) Information on the number of fish landing sites on the basin lakes; b) Information on the facilities available at the fish landing sites to service the fisheries sector ; c) Information on the number of fishers; d) Information on the number and types of fishing crafts; e) Information on the modes of propulsion of the fishing crafts; f) Information on the number types and sizes of fishing gears including the number of illegal fishing gears in the fishery; and g) Recommendations on development and management of the fisheries of the Edward and George lakes and Kazinga channel. h) Beach values in terms of annual catches and annual revenue from the water bodies.

Fisheries studies on Lake George and Kazinga Channel: first quarter final report June/July 2001

FIRRI surveyed the fisheries of Lake George and Kazinga Channel between 20th June and 20th July 2001. This was the second survey FIRRI has conducted for the ILM project on the water system. The first survey was conducted during November 2000. These data, the analyses and accompanying reports contribute to baseline information for the fishery being collected with the support of ILM that is required for lakewide planning and management. Eight fish landing sites (6 on Lake George) namely; Kahendero, Hamukungu, Kasenyi, Kashaka, Mahyoro, Kayinja (2 on Kazinga Channel) namely; Katunguru -K and B fall within the focus of ILM and were surveyed during November 2000 and June/July 2001 over a three day period at each landing site in 2001 (Mahyoro 2 days). In November 2000, each landing was sampled once. FIRRI conducted a rapid FS and concurrently a CAS. All results are reported by landing site and then summed up (Global) for 8 sites on Lake George and Kazinga Channel.

Study on the reproductive biology of Pinctada fucata (Gould) (Mollusca: Pteriidae)

Annual cycle of gonad development and spawning in pearl oyster, Pinctada ficata (Gould) in Nakhiloo, Northeast Persian Gulf, was investigated over two years from August 1994 to June 1996. Gonadal condition was assessed by staging criteria to describe gametogenic development from histological preparations of randomly collected individuals of all sizes. A bimodal gametogenic pattern with summer and autumn spawning periods was evident throughout the study. Gametogensis commenced in November-December which proceeded by major gonadal maturation during February-April. Summer spawning was observed from April to July with major spawning at the latter end. During spawning peak in July, low level of gametogensis was noticed. Gametogenic activity was picked up again in August-September which proceeded by autumn spawning from September to December. Towards the end of spawning season, incidence of gonadal inactivation increased. Minimum level of gonadal activity was observed in November. Temperature regime appears to have influential role in regulation of gametogenic and spawning processes. Gonadal development and spawning trends were similar in both sexes. P. radiaata was found to be protandrous hermaphrodite which matured as a male at shell height greater than 20 mm. Biseivality was uncommon and the sex ratio was about 1:1. Ultrastructure of gametes were investigated in the Pictada fucata (Gould). "Auxiliary cells" closely accociated with developing oocytes were observed. Each oocyte seems to be associated with only one secretory cell. which is characterized by an abundant rough endoplasmic reticulum at the onset of vitellogenesis. Contact between this cell and a developing oocytes is maintained by a desmosome-like junction which can be observed when the vitelline coat is formed. these "auxiliary or nursing cells" seem to play a tropic role in vitellogenesis, and may be involved in the formation of the vitelline coat of the oocytes. Oocytic degeneration is observed in this species, it is a continuous phenomenon of varing intensity throughout the year. The ultrastructural changes resulting in lysis of the oocyte are described. Mature spermatozoa consist of a broad, cap-shaped acrosomal vesicle, subacrosomal material, a round nucleus, two triplet substructure centrioles surrounded by four spherical mitochondria, and a flagellum anchored to the distal centriole and plasma membrane. Spermatozoa of Plucata closley resemble to those of other investigated Pteriidae. Changes in proximate composition of soft tissue and gonadal cycle of Pinctada fucata was studied. Mobilization and utilization of stored reserves are apparent during gametogenesis and gonadal maturation. Protein reserves are utilized during spermatogenesis while reserved carbohydrates form the main energy donor in oogenesis. The role of lipid as am.: energy reserve is second to that of carbohydrate.

Assessment of the performance of beach management units (BMUs) on Lakes Victoria, Albert, Kyoga and George

Until the late 1990s the fisheries of Ugandan lakes had been managed by government where stakeholders were excluded from the decision-making process. In order to involve other stakeholders, co-management was adopted. Operationalising Co-management on landing sites has led to the formation of BMUs at gazetted landing sites. A BMU is made up of a BMU assembly and the BMU committee that it elects. A BMU committee should be: 30% boat owners; 30% boat barias 30% including fish processors, boat makers, local gear makers and repairers, fishing input dealers and managers and 10% fish mongers/traders; and if possible, 30% women. To operate at a particular landing site, one must be registered with the BMU. The BMU assembly is the supreme organ of a BMU empowered to elect, approve and remove the BMU committee

The fisheries and fish stocks of Lake George: their productivity, exploitation, management and conservation

The study was confined to the fisheries of Lake George. The fishery of Lake George has been exploited under controlled exploitation but the permitted number of boats was fixed in the 1950s before the human population increased to the current level. Many more people were involved in fishing and it was feared that the fish stocks might not support the human population. The assignment involved preparation of a research proposal, collection of field data and production of a report in a period of eight months.

The commercial fishery of Lake George, Uganda (East Africa)

A shallow, highly productive, tropical lake is descrihed with a brief history of its commercial fishery. Three separate assessments of the present (1967-1970) yield are compared, with an apparent confirmation of the values derived from Fishery Department statistics over a period of 20 years. The seasonal change in the catch is noted with, an apparent anomaly shown by ohservations of canoe landings. Long-term trends during the period 1950-1969 are considered with a brief discussion of possible future trends in the fishery.

Fish exploitation and changes in the fish community of Lake George, Uganda

Unlike Lake Victoria, the fisheries of Lake George have undergone gradual changes in the size and proportion of the major commercial fish species, the Nile tilapia (Oreochromis niloticus: cichlidae) in the last 40 years (1950-1989). The size decreased from an average weight of 900g in 1950 to 430g in 1989 while percentage contribution in commercial catches during the same period declined from 92% to 36%. The over all annual commercial catches though showed a steady increase from the period 1950 when the fishery was opened to intensive and controlled exploitation, consistently high catches were observed in the 1960s and 1970s followed by a general decline in the early 1980s to amore or less stable fishery in the late 1980s. These changes are attributed to increased fishing pressure especially on the nil tilapia and to increased use of smaller gill net mesh sizes lower than the recommended 127mm mesh. The changes in gill net mesh have brought O. leucostictus, acichlid, into commercial catches confirming that the 88.9mm mesh size nets are used by the commercial fishermen to harvest smaller fish species. The commercial catches are presently dominated by the piscivorous fishes,(over 60%) whose contribution was less than 10% during initial exploitation of the virgin fishery in 1950.The piscivorous fish are mainly caught using hooks and lines. The entire fishery is believed to be exploited close to the maximum. The above trends serve to show the impact of exploitation on fish species diversity. Quantitive and qualitative changes of the major fish species on lake George are due to exploitation pressure unlike Lake Victoria where it is a combination of both exploitations and impact of fish introductions. There has been no fish introduction in Lake George.