Search results for "fishery"
showing 10 items of 591 documents
Long-term dynamics of pelagic fish density and vendace (Coregonus albula (L.)) stocks in four zones of a lake differing in trawling intensity
2001
– An 11-year time series of hydroacoustic fish density estimates and fisheries statistics of vendace (Coregonus albula (L.)) from four zones of a lake differing in trawling intensity was analyzed in order to test the hypothesis that intensive trawling has detrimental effects on pelagic fish stocks, especially vendace recruitment. The standardized fish density estimate in trawled zones showed no decrease in comparison to the non-trawled zone. No signs of recruitment failure associable with trawling intensity were found. The growth of vendace at the end of the study period was slower than that at the beginning, indicating a higher density, most clearly so in the zone with highest trawling int…
Genetic-based evaluation of management units for sustainable vendace (Coregonus albula) fisheries in a large lake system
2022
Abstract The goal of the processing industry, trade and consumers is to get eco-labelled freshwater fish products from sustainable fisheries into the market as soon as possible. The fourth largest natural lake system in Europe, the Saimaa lake system supports a fishery for vendace (Coregonus albula). Certification of the fishery requires an understanding of population structure to help determine the number and spatial extent of management units. In this study, we analysed the genetic diversity of local vendace populations in the Saimaa lake system and aimed to identify the conservation and management units of vendace. Within the Saimaa, the genetic divergence between local populations of ve…
Biomanipulating the drinking water reservoir of Estonia's capital city: Prospects for success
2008
The possibility of utilizing biomanipulation to improve the water quality of Tallinn's drinking water reservoir (Lake Ulemiste) was analysed on the basis of water quality data, test fishing by different methods, and earlier studies on aquatic plants, light climate and sediments. Eutrophic, polymictic Lake Ulemiste is characterized by a prevalence of high filamentous cyanobacteria biomass, rotifers in the zooplankton community, mature bream in the fish biomass, and a high density of planktivores (YOY perch). Several prerequisites for being a potential target for biomanipulation were identified, including (i) decreased external total phosphorus (TP) loading; and (ii) a sufficient stock of pis…
Mortality of pike-perch (Stizostedion lucioperca), brown trout (Salmo trutta) and landlocked salmon (Salmo salar m. sebago) caught as by-catch in pel…
2000
Altogether 146 pike-perch, 49 brown trout and 19 landlocked salmon were caught in 23 exploratory trawl-hauls in lake Pyhaselka, Finland. Brown trout and salmon were caught only in surface trawling, whereas pike-perch were taken also in mid-water trawling. Most of the fish were smaller than the minimal legal size of 40 cm. To estimate their post-trawling mortality, 129 fish were kept in net cages for 1 week. Less than 15% of the pike-perch and brown trout caught by surface trawl died during 1 week caging, whereas every caged salmon died. Mid-water trawling was far more lethal to pike-perch than surface trawling. We conclude that pike-perch and brown trout can recover from surface trawling. S…
Local recruitment of Atlantic cod and putative source spawning areas in a coastal seascape
2021
Abstract Increased knowledge on connectivity is crucial to our understanding of the population dynamics, genetic structure, and biogeography of many coastal species. In coastal marine populations, the main factor for structuring is thought to be the degree of isolation and confinement, limiting genetic exchange between populations. However, many offshore populations use the coastal areas as nursery grounds, but venture back to natal spawning grounds as adults. Therefore, increased knowledge on the connectivity between coastal and offshore populations is crucial to ensure correct assessment of coastal living resources. Here, we combine genetic assignment data of Atlantic cod recruits sampled…
Harvest Pressure on Coastal Atlantic Cod (Gadus morhua) from Recreational Fishing Relative to Commercial Fishing Assessed from Tag-Recovery Data
2016
- Marine recreational fishing is a popular outdoor activity. However, knowledge about the magnitude of recreational catches relative to commercial catches in coastal fisheries is generally sparse. Coastal Atlantic cod (Gadus morhua) is a target species for recreational fishers in the North Atlantic. In Norway, recreational fishers are allowed to use a variety of traps and nets as well as long-line and rod and line when fishing for cod. From 2005 to 2013, 9729 cod (mean size: 40 cm, range: 15–93 cm) were tagged and released in coastal Skagerrak, southeast Norway. Both high-reward (NOK 500) and low-reward tags (NOK 50) were used in this study. Because some harvested fish (even those posting h…
An optimised multi-host trematode life cycle: fishery discards enhance trophic parasite transmission to scavenging birds
2016
Overlapping distributions of hosts and parasites are critical for successful completion of multi-host parasite life cycles and even small environmental changes can impact on the parasite's presence in a host or habitat. The generalist Cardiocephaloides longicollis was used as a model for multi-host trematode life cycles in marine habitats. This parasite was studied to quantify parasite dispersion and transmission dynamics, effects of biological changes and anthropogenic impacts on life cycle completion. We compiled the largest host dataset to date, by analysing 3351 molluscs (24 species), 2108 fish (25 species) and 154 birds (17 species) and analysed the resultant data based on a number of …
The Developmental Contribution From Mobile Phones Across the Agricultural Value Chain in Rural Africa
2011
Published version of an article from the journal: The Electronic Journal of Information Systems in Developing Countries. Also available fro the publisher: http://www.ejisdc.org/Ojs2/index.php/ejisdc/article/viewFile/849/377 The most widespread information and communication technology (ICT) in developing countries today is the mobile phone. The majority of people in the least developed countries still live in rural areas and their livelihood depends on the primary industries. This study investigates the use of mobile phones among farmers in rural Tanzania in order to supply empirical data on the developmental role of this technology. The results show that the improved access to communication…
The effects of oil spills on marine fish: Implications of spatial variation in natural mortality.
2017
The effects of oil spills on marine biological systems are of great concern, especially in regions with high biological production of harvested resources such as in the Northeastern Atlantic. The scientific studies of the impact of oil spills on fish stocks tend to ignore that spatial patterns of natural mortality may influence the magnitude of the impact over time. Here, we first illustrate how spatial variation in natural mortality may affect the population impact by considering a thought experiment. Second, we consider an empirically based example of Northeast Arctic cod to extend the concept to a realistic setting. Finally, we present a scenario-based investigation of how the degree of …
On the adenosintriphosphatase activity of the particulates of the egg of the sea urchinParacentrotus lividus
1957
I particolati delle uova vergini di riccio di mare possono essere separati, a mezzo della centrifugazione differenziale, in due frazioni, una fortemente ed una scarsamente pigmentata. La prima mostra una attivita ATPasica attivata da Mg con un massimo a pH 8.2; il massimo della seconda e invece a pH 6.4. Nelle preparazioni contenenti i due tipi di particolati si ritrovano i due massimi.