Eine zusätzliche Möglichkeit für die Ostseedorsch-Fischerei: Steerte aus 90° gedrehtem Netztuch

In 2004, comparative selectivity investigations were made with the now legal BACOMA codend of 110 mm mesh opening and alternative codends made of netting turned 90° of similar mesh openings on both commercial boats and on research vessels. The results show a certain variability of the BACOMA results – depending on ship type and season (L50 varying between 36,8 and 40,6) – and a general equal efficiency of codends made of netting turned 90° of the same mesh opening. Underwater observations and reduced performance of codends of equal circumference in meshes as the joining round at the end of the tapered part of the trawl indicate the need to reduce the relation of the cir-cumferences of codend and extension to 1 to 0.7 to achieve optimum fit and selectivity.

Climate change adaptation through coastal and use management: The context of environmental justice

Despite an increasing literary focus on climate change adaptation, the facilitation of this adaptation is occurring on a limited basis (Adger et al. 2007) .This limited basis is not necessarily due to inability; rather, a lack of comprehensive cost estimates of all options specifically hinders adaptation in vulnerable communities (Adger et al. 2007). Specifically the estimated cost of the climate change impact of sea-level rise is continually increasing due to both increasing rates and the resulting multiplicative impact of coastal erosion (Karl et al., 2009, Zhang et al., 2004) Based on the 2007 Intergovernmental Panel on Climate Change report, minority groups and small island nations have been identified within these vulnerable communities. Therefore the development of adaptation policies requires the engagement of these communities. State examples of sea-level rise adaptation through land use planning mechanisms such as land acquisition programs (New Jersey) and the establishment of rolling easements (Texas) are evidence that although obscured, adaptation opportunities are being acted upon (Easterling et al., 2004, Adger et al.2007). (PDF contains 4 pages)

Social structure and underwater behavior of harbor seals in southern Monterey Bay, California

To understand harbor seal social and mating strategies, I examined site fidelity, seasonal abundance and distribution, herd integrity, and underwater behavior of individual harbor seals in southern Monterey Bay. Individual harbor seals (n = 444) were identified by natural markings and represented greater than 80% of an estimated 520 seals within this community. Year to year fidelity of individual harbor seals to southern Monterey Bay coastline was 84% (n = 388), and long-term associations (>2 yrs) among individuals were common (>40%). Consistent with these long-term associations, harbor seals were highly social underwater throughout the year. Underwater social behavior included three primary types: (1) visual and acoustic displays, such as vocalizing, surface splashing, and bubble-blowing; (2) playful or agonistic social behavior such as rolling, mounting, attending, and biting; and (3) signal gestures such as head-thrusting, fore-flipper scratch~ng, and growling. Frequency of these types of behavior was related to seal age, gender, season, and resource availability. Underwater behavior had a variety of functions, including promotion of learning and social development, reduction of aggression and preservation of social bonds by maintaining social hierarchy, and facilitation of mate selection during breeding season. Social behavior among adult males was significantly correlated with vocalization characteristics (r = 0.99, X2 = 37.7, p = 0.00087), indicating that seals may assess their competition based on underwater vocalization displays and adopt individual strategies for attracting females during breeding season based on social status. Individual mating strategies may include defending underwater territories, using scramble tactics, and developing social alliances. (PDF contains 105 pages)

River Ure: fisheries drought report 1996

Yorkshire Water Services (YWS) are currently granted a Time Limited Licence (TLL) for abstraction at Kilgram Bridge which is due for renewal in 1999. The Environment. Agency requires information on fish populations with regards to drought conditions and any possible effects that abstraction may have when considering licence renewal. In' order to evaluate any effects of drought and abstraction a three year study was instigated to examine fish populations. Surveys were conducted at nine main River Ure sites and two tributaries in which the triennial rolling programme formed the basis of site selection. Multi-method sampling techniques were carried out at several sites in order to evaluate capture efficiency. High densities of brown trout juveniles were observed in the tributaries with an indication that fish had become crowded as a result of low flows. Recruitment of brown trout in the tributaries was not directly related to flow levels in the main R. Ure. However, it is concluded that salmonids are at risk during drought flows and high temperatures from increased susceptibility to disease, predation, poor water quality and the direct lethal effect of high temperatures in shallow water.

River Ouse: fisheries drought report 1996

The basis for undertaking this study was to examine factors and potential impacts affecting fish and fishing in relation to low flow drought conditions and what other impacts may arise as a result of further reduced flows resulting from abstraction. The study formed the basis of a three year project to concentrate on effects relating to potable water abstractions at Moor Monkton by YWS. To fully evaluate the possible effects on fisheries the study set out to encompass fish population surveys from fry to adult stock, analysis of angler catch data, reports from anglers and river reports from Environment Agency Fisheries staff. In order to evaluate any effects of drought and abstraction a three year study was instigated to examine fish populations. Fish population surveys were conducted at six sites in which the triennial rolling programme formed the basis of site selection. Multi-method sampling techniques were carried out at several sites in order to evaluate capture efficiency. Roach were prolific above the weir at Linton-on-Ouse, with gudgeon, perch and small bream also well represented. Roach dominated catches on the R.Ouse below Linton, with perch and bleak also relatively abundant. Low flows were not thought to be directly correlated to successful recruitment of coarse fish, rather the associated high temperatures during drought conditions showing a strong positive effect with most species exhibiting growth rates above their long-term average. At this stage in the study there are no clear indications that the drought has caused any deleterious effects to coarse fish populations or marked changes in species composition, with evidence of good recruitment by several species, indicating that the higher temperatures have generally been beneficial to recruitment. However, the indication that dace did not benefit as well as other coarse fish under these conditions may suggest some species are affected more than others. The successful strong recruitment of most coarse fish suggests that, in future, fisheries will be supported by the 1995 year-class.