Search results for "Fish"
showing 10 items of 3164 documents
Nested assemblages resulting from host size variation: the case of endoparasite communities in fish hosts
2001
Nested species subsets are a common pattern in many types of communities found in insular or fragmented habitats. Nestedness occurs in some communities of ectoparasites of fish, as does the exact opposite departure from random assembly, anti-nestedness. Here, we looked for nested and anti-nested patterns in the species composition of communities of internal parasites of 23 fish populations from two localities in Finland. We also compared various community parameters of nested and anti-nested assemblages of parasites, and determined whether nestedness may result simply from a size-related accumulation of parasite species by feeding fish hosts. Nested parasite communities were characterised b…
Do small marinas drive habitat specific impacts? A case study from Mediterranean Sea.
2011
Many human activities add new structures to the marine landscape. Despite the fact that human structures cause some inevitable impacts, surprisingly little information exists on the effects of marina on natural marine assemblages. The aim of this paper is to assess habitat-specific response of benthic sessile organisms of rocky shores in relation to the presence of a small marina. Sampling was carried out at three coastal habitats (midshore, lowshore and subtidal) by means of visual censuses adopting an after-control-impact (ACI) experimental design. It appears that the marina affects the structure and composition of benthic communities of both the midshore and the lowshore. Little effect w…
Deep-sea shrimp fishery in Sicily: The economic performance of the shrimp trawling fleet in the ports of Mazara del Vallo, Sciacca, and Porto Empedoc…
2006
Shrimp fishing in Sicily is carried out by fishing companies using trawlers and multifunctional vessels equipped with trawling nets, in a complex and worrisome context, because of the decrease in catch over the last few years. After analysing the structural characteristics of Sicilian trawling, the study concentrates on the three most important shrimp fishing ports in Sicily: Mazara del Vallo, Sciacca, and Porto Empedocle. For each fleet, through a sample analysis, economic performance has been evaluated for the period from 2001 to 2003. Finally, a comparative analysis of the economic performance of the surveyed companies is carried out through a comparison of daily economic productivity in…
Effects of fish feeding by snorkellers on the density and size distribution of fishes in a Mediterranean marine protected area
2005
Although there is a great deal of evidence to show that supplementary feeding by humans in terrestrial environments causes pronounced changes in the distribution and behaviour of wild animals, at present very little is known about the potential for such effects on marine fish. This study evaluated the consequences of feeding by snorkellers on fish assemblages in the no-take area of the Ustica Island marine protected area (MPA; western Mediterranean) by (1) determining if reef fish assemblage structure is affected in space and time by tourists feeding the fish; (2) assessing the effects of feeding on the abundance of the most common fish species; and (3) assessing the effects of feeding on t…
Feeding habits of the spotted flounder Citharus linguatula off the eastern coast of Spain
1994
The composition of the diet of Citharus linguatula (L.) off the coast of the Gulf of Valencia, Spain, was determined between October 1989 and October 1990. The percentage of empty stomachs remained constant throughout the year, except for the period August to September, when a maximum was recorded coinciding with the reproductive period. Crustaceans (Mysidacea and Decapoda) and teleosts constituted the main prey. The composition of the prey ingested varied with predator size; small specimens contained a greater number of mysids in their stomachs, while decapods and fishes were more abundant in the stomachs of larger specimens. Diets varied seasonally: mysids were more important during autum…
Recreational fish feeding affects coastal fish behavior and increases frequency of predation on damselfish (Chromis chromis) nests
2006
Wildlife feeding has become an integral part of the range of activities offered to protected area visitors. In marine protected areas (MPAs), fish feeding may cause changes in the behavior, and thus the density and distribution, of coastal fish species. We evaluated spatial variability in human-positive fish behavior around the Ustica Island MPA (Italy) and the potential indirect effects of behavioral change on other species. Two mensurative experiments demonstrated that ca. 1/3 of the species present in fish-feeding areas exhibited human-positive behavior, losing instinctive fear in the presence of humans and encircling people in the water even when food was not provided. A manipulative ex…
Loss of a freshwater copepod species from El Junco Lake, Galápagos following the introduction and eradication of the Nile tilapia
2021
An undescribed diaptomid copepod probably belonging to a new Mastigodiaptomus species has been discovered and was very abundant in El Junco Lake (San Cristóbal Island, Ecuador) from 1966 until 2004. The species was not found in samples from 2007, 2008 or 2018. The loss of this key species from the lake coincides with the illegal introduction of Nile tilapia to El Junco Lake in 2005 and its subsequent eradication in 2008. The disappearance of this biogeographically and ecologically important copepod population may be explained by direct mechanisms of predation and competition, by a combination of both processes, and by indirect mechanisms linked to alterations in the lake ecosystem. The effe…
Accurate Wound and Lice Detection in Atlantic Salmon Fish Using a Convolutional Neural Network
2022
The population living in the coastal region relies heavily on fish as a food source due to their vast availability and low cost. This need has given rise to fish farming. Fish farmers and the fishing industry face serious challenges such as lice in the aquaculture ecosystem, wounds due to injuries, early fish maturity, etc. causing millions of fish deaths in the fish aquaculture ecosystem. Several measures, such as cleaner fish and anti-parasite drugs, are utilized to reduce sea lice, but getting rid of them entirely is challenging. This study proposed an image-based machine-learning technique to detect wounds and the presence of lice in the live salmon fish farm ecosystem. A new equally di…
Differences in parasite community composition support ecological differentiation in a freshwater gadoid fish
2022
Several northern freshwater fishes have gone through rapid adaptive radiation after the last glacial period, resulting in new species or intraspecific morphs with distinct life histories. Parasite infections can promote adaptive radiations and spatiotemporal differences in patterns of infections can potentially reveal incipient or ongoing speciation processes. We investigated intraspecific differentiation in a freshwater gadoid fish, burbot (Lota lota), by exploring differences in parasite infections between two potential life-history morphs in Lake Konnevesi, Central-Finland, one reproducing species characteristically in shallow littoral waters in February and the other possibly in deep pr…
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…