A survey of the artisanal fishery on the Zimbabwean side of Lake Kariba

Two types of fishermen have been identified along the lake shore: contract fishermen and independent fishermen. Independent fishermen move from their fishing grounds to other grounds in search for more fish and also to communal lands for farming during the rains. The fish from Kariba are marketed to a large part of the country creating a very large market potential. Profits accruing to the fishermen are not very attractive and could be the reason for the migratory behaviour of the fishermen. The fishermen population is rural with a characteristic expansive pyramid.

Electrofishing survey of the River Calder and its tributaries - April 1978.

An electrofishing survey was undertaken in the period April 24th - 28th as part of the detailed biological study of the Calder Catchment being carried out by this department in early 1978. The sites to be fished were selected to indicate broadly the fishing status of the major sections of the main river and its larger tributaries and by no means intended to describe the fishing status of the whole catchment in detail. The results on the distributions of fish species are discussed, in general, in relation to the major polluting influences on the catchment. The results of the second survey are given and discussed separately in Appendix I.

Electrofishing, survey of Skirden and Swanside Beck August/September 1987.

As a follow up survey, the report assesses Skirden and Swanside Beck (North West England) in order to determine: 1. The status of these systems as salmonid nursery streams. 2. The success of planting with salmon fry and parr, carried our earlier in the year. The report gives methods, results, a summary and the author's recommendations.

River Ribble sheep dip incident September 1997. Electric-fishing survey report

This report summarises the findings of a series of electric-fishing surveys carried out at four sites on the River Ribble from September 1997 to September 1998. The aims of these surveys were to assess the impact on juvenile salmonids of a pollution incident involving Synthetic Pyrethrin (SP) that occurred near High Birkwith I (SD 802 767) in September 1997.One of these sites was 2.65km upstream of the pollution whilst the remaining three were at varying distances downstream. Data was collected during surveys of the River Ribble in 1992, 97 and 98. The 1997 and 1998 surveys were carried out specifically to monitor for any possible effects of the SP discharge. Data are shown as grades derived from the National Fisheries Classification scheme (NFC). Results are given for the four salmonid life stages; 0+ trout, >0+ trout, 0+ salmon, >0+ salmon and also Total Salmonids.

Report on eight weeks at the Fisheries Department of the Lancashire River Authority [including a Leeds / Liverpool Canal survey]

This report looks at the interests of the Fisheries Department for the Lancashire River Board, focusing on the Liverpool and Leeds Canal Survey. It looks at finding parasites in fish from an electrofishing survey (roach and perch). This was to contribute towards the main survey with a possible view to suggesting whether or not the parasites were one reason for the poor fish population. Methods of finding parasites are given, and results of what parasites that were found in the fish are discussed.

Variations in eastern North Pacific demersal fish biomass based on the U.S. west coast groundfish bottom trawl survey (2003–2010)

In response to declining biomass of Northeast Pacific groundfish in the late 1990s and to improve the scientific basis for management of the fishery, the Northwest Fisheries Science Center standardized and enhanced their annual bottom trawl survey in 2003. The survey was expanded to include the entire area along the U.S. west coast at depths of 55–1280 m. Coast-wide biomass and species richness significantly decreased during the first eight years (2003–10) of this fishery-independent survey. We observed an overall tendency toward declining biomass for 62 dominant taxa combined (fishery target and nontarget species) and four of seven subgroups (including cartilaginous fish, flatfishes, shelf rockfishes, and other shelf species), despite increasing or variable biomass trends in individual species. These decreases occurred during a period of reduced catch for groundfish along the shelf and upper slope regions relative to historical rates. We used information from multiple stock assessments to aggregate species into three groups: 1) with strong recruitment, 2) without strong recruitment in 1999, and 3) with unknown recruitment level. For each group, we evaluated whether declining biomass was primarily related to depletion (using year as a proxy) or environmental factors (i.e., variation in the Pacific Decadal Oscillation). According to Akaike’s information criterion, changes in aggregate biomass for species with strong recruitment were more closely related to year, whereas those with no strong recruitment were more closely related to climate. The significant decline in biomass for species without strong recruitment confirms that factors other than depletion of the exceptional 1999 year class may be responsible for the observed decrease in biomass along the U.S. west coast.

Statistical inference about the relative efficiency of a new survey protocol, based on paired-tow survey calibration data

Paired-tow calibration studies provide information on changes in survey catchability that may occur because of some necessary change in protocols (e.g., change in vessel or vessel gear) in a fish stock survey. This information is important to ensure the continuity of annual time-series of survey indices of stock size that provide the basis for fish stock assessments. There are several statistical models used to analyze the paired-catch data from calibration studies. Our main contributions are results from simulation experiments designed to measure the accuracy of statistical inferences derived from some of these models. Our results show that a model commonly used to analyze calibration data can provide unreliable statistical results when there is between-tow spatial variation in the stock densities at each paired-tow site. However, a generalized linear mixed-effects model gave very reliable results over a wide range of spatial variations in densities and we recommend it for the analysis of paired-tow survey calibration data. This conclusion also applies if there is between-tow variation in catchability.

Comparison of survey methods for estimating abundance of harbor seals (Phoca vitulina) in glacial fjords

The importance of glacial ice habitats to harbor seals (Phoca vitulina) in Alaska has become increasingly apparent. However, enumerating harbor seals hauled out on ice in glacial fjords has been difficult. At Johns Hopkins Inlet in Glacier Bay, Alaska, we compared a shore-based counting method to a large-format aerial photography method to estimate seal abundance. During each aerial survey, shore-based observers simultaneously counted seals from an observation post. Both survey methods incurred errors in double-counting and missing seals, especially when ice movements caused seals to drift between survey zones. Advantages of shore-based counts included the ability to obtain multiple counts for relatively little cost, distinguish pups from adults, and to distinguish mobile seals from shadows or glacial debris of similar size. Aerial photography provided a permanent record of each survey, allowing both a reconciliation of counts in overlapping zones and the documentation of the spatial distribution of seals and ice within the fjord.

Whole-gear efficiency of a benthic survey trawl for flatfish

Whole-gear efficiency (the proportion of fish passing between the otter doors of a bottom trawl that are subsequently captured) was estimated from data collected during experiments to measure the herding efficiency of bridles and doors, the capture efficiency of the net, and the length of the bridles sufficiently close to the seafloor to elicit a herding response. The experiments were focused on four species of flatfish: arrowtooth flounder (Atheresthes stomias), flathead sole (Hippoglossoides elassodon), rex sole (Glyptocephalus zachirus), and Dover sole (Microstomus pacificus). Whole-gear efficiency varied with fish length and reached maximum values between 40% and 50% for arrowtooth flounder, flathead sole, and rex sole. For Dover sole, however, whole-gear efficiency declined from a maximum of 33% over the length range sampled. Such efficiency estimates can be used to determine catchability, which, in turn, can be used to improve the accuracy of stock assessment models when the time series of a survey is short.

A comparison of two fishery-independent survey programs used to define the population structure of American lobster (Homarus americanus) in the Gulf of Maine

The population structure and abundance of the American lobster (Homarus americanus) stock in the Gulf of Maine are defined by data derived from a fishery-independent trawl survey program conducted by the National Marine Fisheries Service (NMFS). Few sampling stations in the survey area are located inshore, in particular along coastal Maine. According to statistics, however, more than two thirds of the lobster landings come from inshore waters within three miles off the coast of Maine. In order to include an inshore survey program, complementary to the NMFS survey, the Maine Department of Marine Resources (DMR) initialized an inshore survey program in 2000. The survey was modeled on the NMFS survey program, making these two survey programs comparable. Using data from both survey programs, we evaluated the population structure of the American lobster in the Gulf of Maine. Our findings indicate that lobsters in the Gulf of Maine tend to have a size-dependent inshore-off-shore distribution; smaller lobsters are more likely to stay inshore and larger lobsters are more likely to stay offshore. The DMR inshore and NMFS survey programs focused on different areas in the Gulf of Maine and likely targeted different segments of the stock. We suggest that data from both survey programs be used to assess the lobster stock and to describe the dynamics of the stock in the Gulf of Maine.

The effect of autotrawl systems on the performance of a survey trawl

Three aspects of a survey bottom trawl performance—1) trawl geometry (i.e., net spread, door spread, and headrope height); 2) footrope distance off-bottom; and 3) bridle distance off-bottom—were compared among hauls by using either of two autotrawl systems (equal tension and net symmetry) and hauls conducted with towing cables of equal length and locked winches. The effects of environmental conditions, vessel heave, crabbing (i.e., the difference between vessel heading and actual vessel course over ground), and bottom current on trawl performance with three trawling modes were investigated. Means and standard deviations of trawl geometry measures were not significantly different between autotrawl and locked-winch systems. Bottom trawls performed better with either autotrawl system as compared to trawling with locked winches by reducing the variance and increasing the symmetry of the footrope contact with the bottom. The equal tension autotrawl system was most effective in counteracting effects of environmental conditions on footrope bottom contact. Footrope bottom contact was most inf luenced by environmental conditions during tows with locked winches. Both of the autotrawl systems also reduced the variance and increased the symmetry of bridle bottom contact. Autotrawl systems proved to be effective in decreasing the effects of environmental factors on some aspects of trawl performance and, as a result, have the potential to reduce among-haul variance in catchability of survey trawls. Therefore, by incorporating an autotrawl system into standard survey procedures, precision of survey estimates of relative abundance

Uso de madeiras da Mata Atlântica em construções históricas no Rio de Janeiro

Com a chegada dos europeus ao Brasil, inicia-se a intensa exploração dos recursos da Mata Atlântica, direcionados primeiramente para uso da coroa e, posteriormente, para os assentamentos populacionais da colônia. As informações sobre o uso de madeiras na época do Brasil-colônia de Portugal (1630-1822) são escassas e se encontram dispersas. Dessa forma, o objetivo deste trabalho foi realizar uma referência cruzada utilizando três diferentes tipos de culturas materiais: documentos históricos, artefatos e paisagem. Tendo como foco as senzalas da Fazenda Ponte Alta no estado do Rio de Janeiro/RJ, relacionou-se os dados históricos sobre o uso de madeiras de construção no período colonial com o conhecimento científico atual sobre a flora de Mata Atlântica, identificando as espécies utilizadas no passado e sua ocorrência nos fragmentos florestais remanescentes. Para tal, foram visitadas bibliotecas nacionais e internacionais; analisadas amostras das madeiras da estrutura das senzalas e realizado um inventário fitossociológico nos fragmentos florestais remanescentes. Como um dos principais resultados, destaca-se o expressivo número de espécies madeireiras da Mata Atlântica que eram utilizadas nas construções do Brasil-colônia. E que a preferência de uso de determinados táxons pertencentes à Leguminosae, Sapotaceae e Lauraceae, reflete a disponibilidade e abundância dessas famílias no Bioma. Das espécies identificadas nas estruturas das senzalas, 68% foram citadas nos documentos históricos como sendo utilizadas em construções no período colonial e 37% dessas, também foram amostradas no inventário fitossociológico realizado. Constatou-se que as espécies utilizadas para construção no Brasilcolônia apresentavam, na maioria, boa qualidade e alta resistência o que lhes conferia uma multiplicidade de uso. Essa demanda, certamente, tem reflexos diretos na distribuição geográfica, no tamanho populacional e no status de conservação atual das espécies. Os resultados indicam, também, que os construtores do período, principais atores da história, detinham o conhecimento necessário à utilização das florestas locais. Assim, os dados obtidos nos diferentes materiais analisados se mostraram complementares e com interação entre si, agregando informação e veracidade aos argumentos inicialmente postulados