Development of the 28-foot inboard-engined fishing boat in Uganda

With the encouraging results of trawling experiments in Lake Victoria, it became apparent early in 1969 that commercial trawling on Lake Victoria might well be a viable economic enterprise. Considerable discussion about the optimum size and type of fishing vessel ensued, and the Fisheries Department decided to commission a number of different prototypes for comparative trials.

Sub lethal mercuric chloride toxicity induced stress related alterations in the epithelial lining of foot of the freshwater mussel Lamellidens marginalis (Lamarck)

Sub lethal (0.2 ppm) mercuric chloride induced stress related histopathological alterations in the epithelial linings of foot (podium) of the edible freshwater mussel Lamellidens marginalis (Lamarck) were studied using histochemical techniques up to 60 days of exposure. The histomorphological changes were manifested only slowly and its intensity was somewhat proportional to the duration of exposure. The immediate response of the exposed mussels was the altered mucous secretion. There was a progressive incorporation of sulphated glycoproteins into the secretory contents of the mucous cells especially in the first half of the experiment. Marked histopathological changes including necrosis, appearance of pyknotic nuclei, sloughing of epithelial cells and appearance of non-tissue spaces, etc., started appearing during the later half of the experiment. The fag end of the experiment, which witnessed prominent histomorphological changes, was accompanied by highly decreased mucous secretion. KEYWORDS: heavy metal toxicity, mercuric chloride, Lamellidens marginalis, freshwater mussel, histopathology.

Hydrologic aspects of freshening upper Old Tampa Bay, Florida

Upper Old Tampa Bay, a 17-square mile area of Old Tampa Bay, Florida, has been proposed for conversion to a fresh-water lake. The amount of runoff to the proposed lake and its chemical quality are both adequate to freshen and sustain a fresh-water lake in this part of the bay. During 1950-66 runoff to the proposed lake, including discharge from Lake Tarpon, would have averaged 134 mgd (million gallons per day) and would have displaced the volume of the proposed lake at normal pool stage (2.5 feet above mean sea level) about 1.7 times per year. Without discharge from Lake Tarpon, the volume of the proposed lake would have been displaced 1.2 times. If the lake level was initially at a normal pool stage during a critically dry year, such as 1956, the proposed lake would have declined 0.25 to 0.5 foot below the minimum design level, (1.5 feet above mean sea level). (44 page document)

Seepage beneath Hoover Dike southern shore of Lake Okeechobee, Florida

Future water needs in southern Florida call for an increase in the storage capacity of Lake Okeechobee. Seepage from the lake is expected to increase as a result of raising the lake level. Data concerning the occurrence and amounts of seepage are needed for the design and operation of flood-control works which will remove excess water from the rich agricultural lands along the southern shore. Intensive studies at five sites along the southern shore of Lake Okeechobee between the Caloosahatchee Canal and the St. Lucie Canal indicate that seepage occurs chiefly through beds of shell and limestone which underlie the Hoover Dike at shallow depth. Seepage rates at the five sites range from about 0.1 to 0.9 cfs per mile per foot of head across the dike. Seepage beneath the 50-mile length of dike should increase from about 22 to 50 cfs if the average stage of the lake is raised from 14 to 16.5 feet. Seepage is greatest between Moore Haven and Clewiston, where deep borrows have been excavated on the landward and lakeward sides of the dike. Most of the seepage from the lake can be controlled by properly spaced toe ditches which would intercept the seepage and return it to the lake. (PDF contains 108 pages.)

A schematic analysis and discussion of species taken by otter trawl net by the research vessel Orion from July, 1965 to June 1966 in the Chesapeake Bay and major tributaries

From July 1965 to June 1964 the Natural Resources Institute's Research Vessel ORION took 16 minute tows with a forty (40) foot otter trawl net at 38 selected locations in Chesapeake Bay from the south of the Potomac River to Turkey Point at the head of the Bay and including some tributaries. Shallow and deep hauls were taken at most stations with depths ranging from 5 to 140 feet. A schematic summary of the 54 different species caught was compared with "Fishes of the Chesapeake Bay" by S. F. Hildebrand and W. C. Schroeder. Sixteen species including five not contained in the above references were selected for discussion. (PDF contains 21 pages)

Benthic sampling program in Biscayne Bay, 1981-1982

The Biscayne Bay Benthic Sampling Program was divided into two phases. In Phase I, sixty sampling stations were established in Biscayne Bay (including Dumfoundling Bay and Card Sound) representing diverse habitats. The stations were visited in the wet season (late fall of 1981) and in the dry season (midwinter of 1982). At each station certain abiotic conditions were measured or estimated. These included depth, sources of freshwater inflow and pollution, bottom characteristics, current direction and speed, surface and bottom temperature, salinity and dissolved oxygen, and water clarity was estimated with a secchi disk. Seagrass blades and macroalgae were counted in a 0.1-m2 grid placed so as to best represent the bottom community within a 50-foot radius. Underwater 35-mm photographs were made of the bottom using flash apparatus. Benthic samples were collected using a petite Ponar dredge. These samples were washed through a 5-mm mesh screen, fixed in formalin in the field, and later sorted and identified by experts to a pre-agreed taxonomic level. During the wet season sampling period, a nonquantitative one-meter wide trawl was made of the epibenthic community. These samples were also washed, fixed, sorted and identified. During the dry season sampling period, sediment cores were collected at each station not located on bare rock. These cores were analyzed for sediment size and organic composition by personnel of the University of Miami. Data resulting from the sampling were entered into a computer. These data were subjected to cluster analyses, Shannon-Weaver diversity analysis, multiple regression analysis of variance and covariance, and factor analysis. In Phase II of the program, fifteen stations were selected from among the sixty of Phase I. These stations were sampled quarterly. At each quarter, five Petite Ponar dredge samples were collected from each station. As in Phase I, observations and measurements, including seagrass blade counts, were made at each station. In Phase II, polychaete specimens collected were given to a separate contractor for analysis to the species level. These analyses included mean, standard deviation, coefficient of dispersion, percent of total, and numeric rank for each organism in each station as well as number of species, Shannon-Weaver taxa diversity, and dominance (the compliment of Simpson's Index) for each station. Multiple regression analysis of variance and covariance, and factor analysis were applied to the data to determine effect of abiotic factors measured at each station. (PDF contains 96 pages)

Configurations and relative efficiencies of shrimp trawls employed in southeastern United States waters

Common shrimp trawl designs employed in the southeastern United States shrimp fishery are the flat, balloon, semiballoon, jib, and super X-3. Recent innovations in trawl design and rigging, including the twin trawl rigging and tongue trawl design, have improved the efficiency of shrimp trawling gear. A description of the construction techniques for the different designs indicate differences which affect gear performance. Measurements of horizontal spread and vertical opening for 76 trawl configurations indicate the relative efficiencies of the different designs. Maximum horizontal spreading efficiency was achieved by the "twin" and "tongue" trawl designs followed by the super X-3, jib, balloon, and semiballoon designs. Designs having the greatest vertical openings were the tongue and flat trawl designs followed by the semiballoon. Maximum total gape dimension was demonstrated by the "Mongoose" tongue trawl. Comparison of trawl spreading efficiency and door area to headrope length ratio indicates that a range of 70-80 in square (per door) of door area is required for each foot of trawl headrope length for maximum efficiency with conventional trawl designs and 66-75 in square per foot of headrope for tongue trawl designs. (PDF file contains 18 pages.)

Auswirkungen der Wassertemperatur auf die Missbildungshäufigkeit pelagischer Fischembryonen

Malformation rates in embryos of dab, whiting, cod, flounder and plaice have been monitored for several years (1984-2006) in the Southern North Sea. For embryos of all species investigated trends for the fluctuation of malformation rates over the time were registered in the areas showing intermediate prevalences at the beginning of the studies in 1984 and maxima in 1987. Thereafter for all species a decrease of malformation rates was found until 2006 excepting an increase in 1996. A significant negative correlation existed between surface water temperature and prevalences of malformed embryos of dab and other species.

Zusammenhang zwischen Schadstoffen aus der Elbe und missgebildeten Fischembryonen in der Deutschen Bucht.

The trends of malformation prevalence in embryos of dab, Limanda limanda, in the southern North Sea after the year 1990 mirrored the drop in major pollutants in the rivers draining into the German Bight. Despite this general decline we detected a pollution event in the southern North Sea in winter 1995/1996 employing the prevalence of malformations in dab embryos as an indicator. An abrupt rise in malformation prevalence in the embryos of dab, corresponded to a dramatic increase in DDT levels in parent fish from the same area, indicating a hitherto unnoticed introduction of considerable quantities of DDT into the system. This input could be traced back to discharges of unknown origen into the River Elbe.

Wassertemperaturen und Häufigkeiten von Mißbildungen pelagischer Fischembryonen

Malformation rates in fish embryos have been monitored for several years in the Southern North Sea. Their occurrence was interpreted to be related to pollution because malformation rates were highest in near coastal waters known to receive high pollution loads. For embryos of all species investigated synchronous trends for the fluctuation of malformation rates over the time were registered in the areas covered with intermediate prevalences at the beginning of the studies in 1984 and maxima in 1987. Thereafter malformation rates of all species decreased significantly followed by an increase in 1996. It was found that a significant negative correlation between surface water temperature and prevalences of malformed embryos of dab (Limanda limanda) and other species existed over time and space. These correlations became increasingly visible with decreasing concentrations of organochlorines in livers of dab. From these findings it is concluded that temperatures possibly predispose developing fish embryos to the impact of pollutants.

The effect of organotin and copper sulfate on the late development and presettlement behavior of the hard clam Mercenaria mercenaria

The effect of organotin compounds and copper, commonly used as antifouling agent, were studied on Mercenaria mercernaria larvae. They were reared under usual hatchery conditions until they reached 190 um in diameter. The larvae were subjected to four compounds, tributylin chloride (TBT), monobutyltin chloride (MBT), trimethyltin chloride (TMT), cupric sulfate (CuSo4) plus control. Mortality was measured at 24, 48 h, and 96h. Behavioral and/or metamorphic changes were recorded in triplicate at 24-48 and 96 h. The appearance in swimming larvae of a functional foot was considered a sign of competence to set and was recorded as a "pediveliger". Swimming larvae were considered as larvae that have not yet reached their total development and they were recorded as "swimming". Larvae that did not show foot or swimming activity and were static but alive on the bottom were recorded as "bottom". TBT was found to completely inhibit swimming activity at sublethal concentrations throughout the period of observation. Copper and MBT inhibited swimming from 48 h, TMT did not inhibit swimming activity at any of the times recorded. The four compounds ranked in order of decreasing toxicity were TBT>TMT>CU>MBT.

Skimmers: Their Development and Use in Coastal Louisiana

The origin, development, and utilization of the skimmer net is reviewed along with other historical shrimp gears used in coastal Louisiana. The skimmer was developed to catch white shrimp, Penaeus setiferus, observed jumping over the cork line (headrope) of trawls being worked in shallow waters. A description of the gear is presented including basic components and various frame designs used by fishermen during its development. The advantages of skimmers over bottom trawls include: multiple use as both trawl and butterfly net (wing net), ease of deployment, increased maneuverability, reduction and greater survivability of bycatch, and ability to cover more area due to increased speed and continuous fishing capability. Disadvantages may include compromising vessel stability when stored upright on the deck, possible damage to water bottoms when improperly rigged, and limitation to a 12-foot (3.6 m) maximum depth due to size restrictions. The growing popularity of the skimmer net is evident by its introduction into North Carolina and inquiries from other southeastern Atlantic and Gulf coast states.

Regional Fisheries Advisory Committee 17th October, 1988

This is the report from the Regional Fisheries Advisory Committee meeting, which was held on the 17th October, 1988. The report contains sections on fisheries byelaws, sea fisheries byelaws, and serious fish mortalities. This section looks at some of the incidents which resulted in the loss of fish such as the River Tame, Stalybridge; Three Pools Waterway, Southport; River Weaver, Winsford to Vale Royal; River Weaver, Nantwich; Colton Beck, Greenodd; River Ribble, Calder Foot to Preston; Trawden Beck and Colne Water. The Fisheries Advisory Committee was part of the Regional Water Authorities, in this case the North West Water Authority. This preceded the Environment Agency which came into existence in 1996.