Search results for "Fish"

Behavioral responses of Atlantic cod to sea temperature changes

2015

Understanding responses of marine species to temperature variability is essential to predict impacts of future climate change in the oceans. Most ectotherms are expected to adjust their behavior to avoid extreme temperatures and minimize acute changes in body temperature. However, measuring such behavioral plasticity in the wild is challenging. Combining 4 years of telemetry-derived behavioral data on juvenile and adult (30–80 cm) Atlantic cod (Gadus morhua), and in situ ocean temperature measurements, we found a significant effect of sea temperature on cod depth use and activity level in coastal Skagerrak. During summer, cod were found in deeper waters when sea surface temperature increase…

The Adaptation of Professional Fishing to Diminished Vendace Stocks: The Case of Finnish Inland Waters

1999

Abstract The large number of lakes covering 10% of Finland's surface area provide an opportunity for both full-time and part-time professional fishing. However, the development of the fishing industry is hindered by unpredictable fluctuations in fish stocks, by the elaborate hierarchy of the fisheries system, as well as by certain features of Finnish professional fishing, such as the small size of fishing enterprises, the scattered pattern of production, and long transportation distances to the core demand areas. According to Finnish catch statistics, the stock of vendace Coregonus albula has clearly diminished since the mid 1980s. Our results show that full-time professional fishermen diff…

The desert at Zait Bay, Egypt: a bird migration bottleneck of global importance

2009

The study area at Zait Bay, Egypt (c. 700 km2) is situated in the middle of the West Asian-East African migration flyway used by very large numbers of soaring migrants. At this site the corridor narrows into a bottleneck. There exist only very few bottlenecks of this magnitude in the world. Observations were performed at all hours between sunrise and sunset at 26 observation sites, situated 5 km apart. The northern part of the area under investigation (19 observation sites) was situated within the Gebel El Zeit IBA (criteria A1 and A4iv), while the southernmost part (8 observation sites) was outside. The overall evaluation has shown that 179,681 soaring birds including 122,454 storks and 36…

Pelagic food web as the basis of fisheries in Lake Tanganyika: A bioenergetic modeling analysis

2002

Fisheries in Lake Tanganyika, East Africa, are mainly based on two predominantly planktivorous clupeids (Stolothrissa tanganicae and Limnothrissa miodon) and a centropomid predator (Lates stappersi), caught with lift nets, purse seines, and beach seines by traditional, artisanal, and industrial fishers. The biological basis and sustainability of the present fisheries were assessed in a comprehensive project “Research for the Management of the Fisheries on Lake Tanganyika” in 1992–1998. Production in the whole lake was estimated for the entire pelagic food chain leading to the commercially important fish species. Preliminary calculations based on a constant production efficiency suggested th…

2015

Prey preference of top predators and energy flow across habitat boundaries are of fundamental importance for structure and function of aquatic and terrestrial ecosystems, as they may have strong effects on production, species diversity, and food-web stability. In lakes, littoral and pelagic food-web compartments are typically coupled and controlled by generalist fish top predators. However, the extent and determinants of such coupling remains a topical area of ecological research and is largely unknown in oligotrophic high-latitude lakes. We analyzed food-web structure and resource use by a generalist top predator, the Arctic charr Salvelinus alpinus (L.), in 17 oligotrophic subarctic lakes…

Long-term analysis (1863–2002) of environmental change in the Capo Feto area (Mediterranean sea)

2004

The area of Capo Feto represents one of the few remaining salt-marshy zones in Sicily. It lies within a site of importance for the Community (defined as a “sito di importanza comunitaria” (SIC)), which also includes Margi Spanò and Margi Milo. The Capo Feto and Margi Spanò marshlands have also been identified by the Ministry for the Environment as an area deserving special protection (“zona a protezione speciale” (ZPS)). Moreover, in 1999, 150 ha of the Capo Feto area were included in a project for environmental rehabilitation as part of the European Union “Life-Nature 2000” programme (Comitato Tecnico-Scientifico Area di Capo Feto, 1997). Prior to this, the area had become somewhat degrade…

Bite marks as evidence of predation in early vertebrates

2009

Study of lifetime bite traces on agnathans and fish (or gnathostomes) from Ukraine, Estonia, Latvia and north-western and central European Russia reveals evidence of predator–prey relationships in communities of Devonian age. Numerous bite traces on skeletal parts of agnathan pteraspidiforms and psammosteiforms, placoderm arthrodires and antiarchs and sarcopterygian porolepiforms and osteolepiforms are described. Evidence of healing shows that prey organisms responded to predation by reconstruction of damaged skeletal elements. Ichthyofaunistic analysis is used to establish possible predators. The most probable predators in the Middle and Late Devonian communities are sarcopterygian porolep…

Caging techniques for field exposures of fish to chemical contaminants

2005

The article reviews current state-of-the-art to conduct fish caging as an assessment and monitoring technique in aquatic toxicology. A multitude of scientific, practical and management factors influence and may restrict how field research is carried out. For many purposes the advantages of transplant fish caging outweigh the alternative methodologies of impact studies of xenobiotics. However, besides mortality, virtually no study has evaluated the physiological consequences of caging fish. It is not known how caging itself affects the responses of fishes to chemical pollution. The used caging densities are commonly too high. However, with the aid of variables describing physiological stress…

Comparative immunologic models can enhance analyses of environmental immunotoxicity

1996

Abstract To treat immune systems and how environments affect them is a unique challenge especially when the environment is considered in its broadest perspective: internal and external. Internal focuses on relationships between immune, nervous and endocrine systems (neuroendocrine) and how they interact to maintain homeostasis. External considers physical and chemical influences that act to change the internal. Using animal models is based upon phylogeny which focuses on invertebrates, fish, amphibians, and reptiles, including mammalian results and relationships to humans. Emphasizing primitive animals is due to a growing interest in using them as models, sentinels, surrogates—predictors of…

Dispersal of larval and juvenile seabream: Implications for Mediterranean marine protected areas

2015

International audience; In the marine context, information about dispersal is essential for the design of networks of marine protected areas (MPAs). Generally, most of the dispersal of demersal fishes is thought to be driven by the transport of eggs and larvae in currents, with the potential contribution of dispersal in later life stages relatively minimal.Using otolith chemistry analyses, we estimate dispersal patterns across a spatial scale of approximately 180 km at both propagule (i.e. eggs and larvae) and juvenile (i.e. between settlement and recruitment) stages of a Mediterranean coastal fishery species, the two-banded seabream Diplodus vulgaris. We detected three major natal sources …