We examined the spatial distribution of trawling effort from logbook data from all Icelandic vessels fishing for demersal fish between 1991 and 1997 with a spatial resolution of 1 degree of latitude and 1 degree of longitude. The trawling effort was widely distributed but was intensive only in small and localised areas. Three measures of effort were compared; tow frequency, tow...
A new design for a salmon trap aimed at minimizing damage to catch and gear caused by grey seals was tested. The traditional trap design used in the northern Baltic permits an efficient hunting strategy by seals, whereby chased fish entangle themselves in the side panels and can then easily be taken, with associated damage to the net. The side panels of the test trap (excluding...
We present an application of Bayesian hierarchical modelling of stock–recruitment (SR) relationships aiming at estimating Biological Reference Points (BRP) for European Atlantic salmon (Salmo salar) stocks. The structure of the hierarchical SR model developed distinguishes two nested levels of randomness, within-river and between rivers. It is an extension of the classical Ricker...
Graphical methods are very efficient means for error detection in large volumes of spatial data. Bathymetry data form the basis for nautical charts that are used by the fishing industry to utilize and manage the fishing resources, and by the fishing communities to study migration and habitat studies of fish. The bathymetry data of the world have been collected over a century and...
Traditional acoustic approaches to the estimation of fish biomass have relied upon single-beam echo sounders that sample a relatively small volume of the water column within the survey area. Mean transect values, after bottom removal, are extrapolated to provide an estimate of number or biomass within a survey area. Over the past 20 years, many multibeam sonars have been...
Individual-based models (IBM), as an ecological modeling paradigm, are being used widely in the analysis of fish populations in marine ecosystems. The flexibility and power of IBMs with respect to building detailed and realistic biological models have encouraged recent and important extensions, which include explicit spatial dynamics and biophysical forcing of certain life stage...
Visualization is a very potent tool in the provision of decision support in fisheries information systems. Fisheries management involves distinct groups of participants with a common purpose but different perspectives on strategies to be pursued and the information required for effective management. This paper discusses the visualization capabilities of FishCAM2000 (FC), which is...
Over the past five years we have investigated and used commercial fishing vessels and their associated acoustic hardware as platforms for acoustic surveying and data collection. During this period we developed an automated acoustic logging system that will simultaneously record data from the ship's existing sounder, sonar, and navigation systems. The system was designed to be...
The aim of this paper is to present a tool for the exploratory analysis of trawl survey data using a Geographical Information System (GIS). In particular, the architecture and the main functions of an interactive desktop mapping system, the Trawl Survey Data Viewer (TSDV), are described. The TSDV was developed to provide non-GIS specialists fishery researchers an intuitive...
A digital acoustic seabed classification system, QTC View (Series IV) was used in the coastal waters of Newfoundland to characterize and classify marine benthic habitats. The QTC View system was calibrated in Placentia Bay at sites identified independently during a submersible research program. Four different habitats were used for calibration of the QTC View system: mud, gravel...
Acoustic data from repeated acoustic surveys of a shoal of widow rockfish (Sebastes entomelas) were portrayed as three-dimensional images over an interpolated bathymetric surface. Through development of a number of sub-programs which defined the relationships between different elements of the data, the large data sets could be quickly processed and visualized to gain an...
Acoustic tag systems have been used for many years to study the behavior of fish in specific areas of interest. In particular tag systems are being used successfully to study the behavior of downstream migrating salmon smolts (Oncorhynchus spp.) as they approach hydro-electric dams. While field studies have demonstrated the potential for acoustic tag systems, little has been done...
The abundance of salmon lice was examined in two stocks of sympatric anadromous Arctic char and sea trout in sub-Arctic regions in northern Norway in June, July, and August 1992 and 1993. One stock feeds in a coastal area exposed to moderate salmon farming activity (exposed area), while the other feed in a region without salmon farms (unexposed area). The salmon lice infestation...
The biomass of horse mackerel (Trachurus trachurus) in the North Sea was estimated for the period 1991–1997. Calculation was based on a ratio estimate that related catch per unit effort (cpue) data from scientific surveys of horse mackerel to the cpue data of a reference species from the same surveys. It was assumed that both horse mackerel and the reference species were equally...
Ovigerous female Nephrops were collected by trawl and creel and maintained in individual containers over the nine-month incubation period to investigate aspects of fecundity. Females which extruded eggs in captivity shortly after capture provided an estimate of mean realised fecundity of 104.3 eggs g−1 live weight (s.e.=2.7). Egg loss during incubation, estimated by sampling...
The reproductive success and thus abundance and distribution of dab, plaice, and flounder in the Baltic Sea, a large brackish water area, is restricted by salinity. By measuring spermatozoa mobility and fertilisation rates at different salinities and determining the salinity at which eggs are neutrally buoyant, the salinity requirements for successful egg development were...
Photographic and visual surveys of the whelping (pupping) concentrations off eastern Newfoundland (“Front”) and in the Gulf of St Lawrence (“Gulf”) were conducted during March 1994 to determine whether pup production of Northwest Atlantic harp seals has increased since the decline in hunting during the mid-1980s and early 1990s. Photographic counts were corrected for...
Whale displacement by acoustic “pollution” has been difficult to document, even in cases where it is strongly suspected, because noise effects can rarely be separated from other stimuli. Two independent studies on the natural history of killer whales (Orcinus orca) monitored frequency of whale occurrence from January 1985 through December 2000 in two adjacent areas: Johnstone...
Using results from annual studies in 1992–1999 in the Barents Sea, the dynamics of Northeast Atlantic minke whale (Balaenoptera acutorostrata) predation upon immature Norwegian spring spawning herring (Clupea harengus) are assessed. Herring spawn along the western coast of Norway, and the larvae are transported northwards to coastal areas of the southern Barents Sea where they...
A model is presented of the annual consumption of prey by seabirds living in the Norwegian and Barents seas (ICES Areas I, IIa, and IIb) based on the numbers of birds present at any one time, their energy expenditure (and hence their food demand), and the composition of their diet. About 20 million seabirds living in the Barents Sea annually consume approximately 1.16×106 t, with...
A 1680 km2 coastal archipelago area in Norway around Sandøy (62°N 6°E), with a resident population of approximately 750 harbour seals was modelled in a geographic information system (GIS). The proportions of different habitat types available to harbour seals for foraging were estimated. Empirical data on levels of activity and foraging of VHF radio-tracked harbour seals were used...
The consumption rate of fishery discards is evaluated and the organisms involved in recycling discarded fish analysed. For this purpose, a fixed baited camera was deployed on the continental shelf and upper slope of the Catalan Sea (northwestern Mediterranean), where trawlers discard large quantities of non-target species. The results showed considerable bait consumption after 12...