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Size Selectivity (size + selectivity)
Selected AbstractsDenil fishway utilization patterns and passage of several warmwater species relative to seasonal, thermal and hydraulic dynamicsECOLOGY OF FRESHWATER FISH, Issue 4 2001C. M. Bunt Abstract , Two different Denil fishways on the Grand River, Ontario, were used as check-points to evaluate the upstream movement of fishes past a low-head weir and to examine the proportions and inferred swimming performance of non-salmonid warmwater fishes that used each fishway type. Traps installed at fishway exits were used to collect fish during 24-hour sampling periods, over 40,51 days each year, from 1995 to 1997. Passage rates, size selectivity, water temperature, water velocity and turbidity for the periods of maximum passage for each year were examined. General species composition from trap samples shifted from catostomids to cyprinids to ictalurids to percids and centrarchids, with some overlap, as water temperatures increased from 8 °C to 25 °C in the spring and early summer. Water depths, and therefore water velocities in each fishway, were independent of river discharge due to variable accumulations of debris on upstream trash-racks. Relationships between the water velocity and the swimming and position-holding abilities of several species emerged. Turbidity was directly related to river discharge and precipitation events, and many species demonstrated maximum fishway use during periods of increased turbidity. This study 1) provided evidence of strongly directional upstream movements among several species that were previously considered non-migratory and 2) describes physical and hydraulic conditions during fishway use for 29 non-salmonid fish species., [source] Electroanalytical Applications of Microporous Zeolites and Mesoporous (Organo)Silicas: Recent TrendsELECTROANALYSIS, Issue 7 2008Alain WalcariusArticle first published online: 10 MAR 200 Abstract Microporous zeolites and ordered mesoporous (organo)silicas have been widely used as electrode modifiers because of their attractive properties (ion exchange and size selectivity of zeolites, well ordered nanoreactors containing a high number of widely accessible active centers in mesoporous (organo)silicas). These properties have been intelligently combined to selected redox processes to improve the response of the resulting modified electrodes or to design novel electrochemical detection schemes. This up-to-date review provides the recent advances made in the electroanalytical applications of zeolite modified electrodes and discusses the interest of ordered mesoporous (organo)silica materials in electroanalysis. [source] Comparison of the size selectivity of diamond (PA) and square (PE) mesh codends for deepwater crustacean species in the Antalya Bay, eastern MediterraneanJOURNAL OF APPLIED ICHTHYOLOGY, Issue 4 2009M. C. Deval Summary The aim of this study was to compare selectivity results of currently used 44 mm nominal polyamide (PA) diamond mesh- and alternatively suggested 40 mm nominal polyethylene (PE) square mesh- codends in the deepwater crustacean trawl fishery in the Antalya Bay, eastern Mediterranean. Selectivity experiments were carried out during targeted trawling of four commonly harvested crustacean species: giant red shrimp Aristaeomorpha foliacea, ,blue and red' shrimp Aristeus antennatus, rose shrimp Parapenaeus longirostris, and pandalid shrimp Plesionika martia. A conventional bottom trawl of 600 meshes around the fishing circle was operated onboard a commercial stern trawler between 6 and 18 June 2007. Depth of the fishing area varied between 441 and 630 m. Data were collected using the covered codend technique, and analyzed using a logistic equation with maximum likelihood for individual and pooled hauls. The commercially used trawl codend was unable to release immature crustaceans. Selectivity parameters of the three species of crustaceans were distinctly lower when collected with the polyamide diamond mesh than with the polyethylene square mesh, except in the case of giant red shrimp for which values were similar. However, the present and previous results show that in square mesh codends, mesh sizes must be more than 40 mm in order to keep catches clear of specimens below minimum landing sizes or 50% sexual maturity sizes of crustaceans in the Mediterranean. This study suggests that regulating mesh size by requiring square mesh openings during deep water crustacean trawling of the eastern Mediterranean is essential for the release of immature individuals. [source] Sorting grid trials to improve size selectivity of red mullet (Mullus barbatus) and annular sea bream (Diplodus annularis) in Turkish bottom trawl fisheryJOURNAL OF APPLIED ICHTHYOLOGY, Issue 3 2008C. Ayd Summary Sorting grids with two different bar spacings (12 mm and 14 mm) were tested to improve size selectivity of the commercially important fish species, red mullet (Mullus barbatus) and annular sea bream (Diplodus annularis), in Turkish bottom trawl fishery. Fishing trials were carried out with R/V ,Egesüf' between April and May 2003 in Izmir Bay, Aegean Sea, using a traditional bottom trawl. Selectivity data were collected by the top cover method and analyzed by means of a logistic equation with the maximum likelihood method. Selectivity parameters for individual hauls were obtained with the software program cc 2000. Mean selectivity was also estimated and compared using the EC Model software that takes between-haul variations into account. The codend catch size as an additional explanatory variable was used in the comparison. The Kolmogorov,Smirnov (K,S) test was also applied to detect differences between length-frequency distributions in the upper and lower bags of the 12 and 14 mm bar spacings for red mullet and annular sea bream. The mean L50 values of red mullet were 8.7 and 10.0 cm with the 12 and 14 mm grids, respectively. The L50 value of 14 mm was comparable with the L50 value of the codend mesh size; however, the 12 mm value was rather low. The mean L50 values of 12 and 14 mm bar spacings were 8.8 and 10.4 cm for annular sea bream, respectively; the value of 14 mm bar spacing was very close to 50% size at sexual maturity of the species (10.5 cm). The K,S test indicated length distributions of red mullet and annular sea bream in the 12 and 14 mm upper and lower bags as significantly different (P < 0.05). These results show that improving the size selectivity in a multi-species fishery using a single selective device is rather difficult. However, higher size selectivity can be obtained when considering the minimum landing size or the 50% sexual maturity size for a given species. [source] Dynamics of black spot sea bream (Pagellus bogaraveo) mean length: evaluating the influence of life history parameters, recruitment, size selectivity and exploitation ratesJOURNAL OF APPLIED ICHTHYOLOGY, Issue 3 2006K. Erzini Summary Stochastic simulations were used to evaluate the influence of recruitment pattern (log-normal, decreasing), size selectivity (normal, logistic model) and fishing mortality pattern (abrupt, continuous increase in fishing mortality) on the evolution of mean length and the dispersion of mean length for a relatively long-lived deep-water species, the black spot sea bream (Pagellus bogaraveo). An abrupt increase in fishing mortality resulted in mean size decreasing and stabilizing at a lower level while a steady increase in fishing mortality caused the continuous decrease in mean size that has been reported for many long-lived species. Decrease in mean size was greatest for logistic model simulations and for cases where fish were susceptible to capture at a small size. Logistic selectivity, with decreasing recruitment and increasing fishing mortality over time, resulted in mean length and variability in mean length trends similar to that observed for the Strait of Gibraltar fishery. Furthermore, it was found with the declining recruitment that moderate increases in fishing mortality can result in significant decreases in mean length. Given the importance of mean size as an indicator of the state of a resource, these simulations are a useful alternative or complement to standard fisheries assessment methods, helping to provide information on exploitation patterns and rates that can be used for conservation and management. [source] Claudin-5 is Restricted to the Tight Junction Region of Uterine Epithelial Cells in the Uterus of Pregnant/Gravid Squamate ReptilesTHE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 5 2008Joanna M. Biazik Abstract Claudin-5, a tight junctional protein associated with ion and size selectivity, has been found in the uterus of skinks. This study has generated critical information about the molecular assembly of the tight junction at various stages of the reproductive cycle in the skink uterus. Recent studies looking at tight junctional proteins found occludin expression in the tight junction region of uterine epithelial cells in the skink uterus; however, occludin did not disclose any further information about the ions and size of ions permeating across the paracellular pathway. A ,22-kDa claudin-5 band was detected in the uterus of the skinks present in this study and immunohistochemistry revealed that claudin-5 redistributes to the tight junction region of the lateral plasma membrane of uterine epithelial cells in late stage pregnancy/gravidity. This finding indicates that the tight junction becomes more assembled to precisely regulate ion and solute permeation in late stage pregnancy/gravidity. Claudin-5 with its functional role as a molecular sieve due to the formation of ion and size selective pores suggests that permeation of ions smaller than 0.8 kDa are restricted when claudin-5 is redistributed to the tight junction region of the later plasma membrane. This report is the first description of the molecular mechanisms that may be involved in regulating nutrient provision in the reptilian uterus. Anat Rec, 291:547,556, 2008. © 2008 Wiley-Liss, Inc. [source] Dynamics of intracohort cannibalism in cultured fishAQUACULTURE RESEARCH, Issue 7 2002E Baras Abstract Cannibalism is a frequent phenomenon in fish, especially in culture environments where fish are unable to escape predation via habitat segregation or migration. Not all cultured fish species start to exhibit cannibalism at the same age or size, nor is cannibalism equally intense in different species or life stages. Predator to prey size ratios vary substantially between species and life stages, chiefly because cannibalism is governed by gape size limitations and allometric growth of mouthparts. The development of sense organs, hard body parts, swimming and escape capacities in both the predator and the prey also influence prey size selectivity. The dynamics of cannibalism are influenced by these, as well as by environmental, factors that have effects on feed intake, growth depensation and facilitate or complicate the displaying of cannibalistic behaviour. Knowledge about cannibalistic behaviour and the logistics of cannibalism along with environmental enhancement are prerequisites for the mitigation of cannibalism in aquaculture. Also, within the context of strain selection, it is of importance to determine whether cannibals are natural-born killers or just lottery winners. These factors are discussed, chiefly as they apply to intracohort cannibalism. In addition, guidelines are suggested for cannibalistic risk assessment, and methods for mitigation of cannibalism are discussed. [source] | |||||||||||||