Search results for "fish"
showing 10 items of 3164 documents
Harnessing productivity potential and rehabilitation of degraded sodic lands through Jatropha based intercropping systems
2016
Abstract This paper evaluates an intercropping model with J atropha curcas L. (JCL) as an alternative crop on degraded sodic land in north India. Monoculture of JCL has not proven economically viable in India in view of its poor yield; therefore, intercrops in between JCL plantations were tried to optimize land use efficiency. The results revealed that the planting of JCL at 3 × 3 m spacing with inter-cultivation of sweet basil–matricaria (SB-M) cropping system for four years was more economically viable than planting at 3 × 2 m spacing and the other rotations tested in the study. Improvements in soil properties in terms of soil pH, EC and organic carbon were found with the SB-M cropping sy…
Does population genetic structure support present management regulations of the northern shrimp (Pandalus borealis) in Skagerrak and the North Sea?
2014
AbstractPopulation structuring in the northern shrimp (Pandalus borealis) in the North Sea area (including Fladen and Skagerrak) was studied by microsatellite DNA analyses. Screening 20 sample locations in the open ocean and Skagerrak fjords for nine loci revealed low, but significant genetic heterogeneity. The spatial genetic structure among oceanic samples of Skagerrak and the eastern North Sea was weak and non-significant, consistent with the current management regime of one single stock. However, Skagerrak fjord samples generally displayed elevated levels of genetic differentiation, and significantly so in several pairwise comparisons with other fjords and oceanic samples. Although the …
Health effects of mercury ingested through consumption of seafood
1995
It is known world-wide literature that seafood consumption is the main source of mercury intake in people not occupationally exposed. Several studies on the presence of mercury in sea water, sediment and fish and its effects on human health have been carried out in many countries in the Mediterranean area such as Greece, Italy and Jugoslavia. Few data have been published on Sicilian coastal population, consumers of high amounts of fish and on seawater status as the starting point of alimentary chains involving marine food. This study was carried out in July 1991 and July 1992 to determine total mercury and methylmercury levels in selected populations of the coast of Sicily: fishermen in a l…
Invasion success despite reduction of genetic diversity in the European populations of eastern mosquitofish (Gambusia holbrooki)
2006
The introduction of a few individuals to new, isolated habitats (founder effect) is expected to reduce the genetic variability of a population. At the beginning of the last century a few eastern mosquitofish (Gambusia holbrooki) individuals were introduced to Southern Europe from North America to control malaria‐carrying mosquitoes. We studied the effect of this severe bottleneck on genetic variability in four populations of eastern mosquitofish introduced to Spain and Italy in the early 1900s and compared them to a native population in North America. Using amplified polymorphic DNA–polymerase chain reaction (RADP–PCR) we found a strong reduction of genetic diversity, in terms of both numbe…
Megabenthos Underwater Video (MUV): a new device to evaluate species distribution in hard-to-reach marine areas
2021
A device, called Megabenthos Underwater Video (MUV), was designed and built for the counting and the size estimate of benthic organisms in hard-to-reach areas. Since 2014 Cassiopea andromeda, an invasive alien jellyfish in the Mediterranean Sea with benthic behavior, colonized a recreational harbor (Cala) of Palermo with a stable population. Studying the species distribution in this area with classical methods (such as visual census, ROV, etc.) was not applicable due to the large presence of obstacles (ropes, anchor cables, boats) and to dive difficulties in these types of area. The MUV was tested from 2017 to 2018 for the study of the spatial-temporal distribution of C. andromeda in the Ca…
Seasonal population dynamics of Zeuxapta seriolae (Monogenea: Heteraxinidae) parasitising Seriola dumerili (Carangidae) in the Western Mediterranean.
2013
We examined the seasonal and yearly population dynamics of the monogenean pathogen Zeuxapta seriolae on juvenile fish from wild populations of Seriola dumerili. The study is based on bimonthly monitoring between April, 2005 and April, 2007 off Majorca, and newly obtained monogenean population data for juvenile fish from three additional localities in the Western Mediterranean (off Alicante, Corsica and Sardinia). We documented the highest intensities and abundances of Z. seriolae, with mean abundance values similar to or higher than those reported in the single case of wild fish mortalities reported to date. There was a recurrent pattern of seasonal change in infection with Z. seriolae in t…
Long-term decrease in sex-specific natural mortality of European lobster within a marine protected area
2013
Marine protected areas (MPAs) and marine reserves hold promise as tools for nature conservation and fisheries management, but data on long-term demographic effects are still sparse. Here, we use a unique capture-mark-recapture data set from Kavra, an MPA on the west coast of Sweden where fishing for European lobster Homarus gammarus has been banned since 1989, to directly quantify annual survival probabilities in the absence of harvest mortality. The non-migratory behaviour of this species allowed multiple recaptures and releases of a large num- ber of individuals within the MPA. We found strong evidence for a long-term decrease in sex - specific natural mortality throughout the study perio…
On the infracommunity structure of adult cestodes in freshwater fishes.
1990
The distribution–co-occurrence and exchange of adult cestode species in two fish communities (the Bothnian Bay and Lake Yli-Kitka both in Finland) was studied. Coexistence of two or more mature cestode species in the same fish host population was zero for all fish species studied (33) except pike in the Bothnian Bay and whitefish in the lake. It was found that 60% of the fish species studied in the Bothnian Bay and 80% of the fish species studied from Lake Yli-Kitka harboured only 1 mature cestode species. Exchange of adult cestode species between the different fish species in these two fish communities was found to be as rare as coexistence. The infra-community structure of adult cestodes …
Spatial ecology of coastal Atlantic cod Gadus morhua associated with parasite load
2015
Acoustic tags and receivers were used to investigate the spatial ecology of coastal Atlantic cod Gadus morhua (n = 32, mean fork length: 50 cm, range: 33–80 cm) on the Norwegian Skagerrak coast in 2012. Monthly home ranges (HR), swimming activity and depth use varied considerably among individuals and through the months of June, July and August. HR sizes for the period ranged from 0·25 to 5·20 km2 (mean = 2·30 km2). Two thirds of the tagged G. morhua were infected with black spot disease Cryptocotyle lingua parasites; these fish had larger HRs and occupied deeper water compared with non-infected fish. The infected fish also tended to be more active in terms of horizontal swimming. From an e…
Predation by signal crayfishPacifastacus leniusculuson fish eggs and its consequences for coregonid recruitment
2015
The character and magnitude of predation by the invasive, ectothermic Pacifastacus leniusculus, a crayfish widely introduced to Europe and Japan from North America, on the eggs of coregonid fishes, vendace Coregonus albula and whitefish Coregonus lavaretus were examined by experimentation, modelling and field data. The present results showed that P. leniusculus has the potential to be very efficient predator of fish eggs under winter conditions, but the predation by P. leniusculus did not significantly decrease production of coregonid larvae during the years with a high P. leniusculus population in the study lake. Hence, the mortality caused by the novel invertebrate predator appeared to co…