Surface wildfire in conifer broad-leaved forests of the Hyrcanian region of Iran: short-term effect on regeneration and damage to trees     

Seyed Abdolkhalegh Yadegarnejad  Mehdi Dylam Jafarabad  Najmeh Mohammadi Savadkoohi 《林业研究》2015,26(2):425-434

Wildfires in recent years have resulted in degradation and damage to the Hyrcanian forest ecosystems in Northern Iran.This study was carried out to investigate fire damage to trees and changes in regeneration in early-season growth after wildfires in the Golestan Province.For this purpose,a random sampling plan was used,with 60 circular plots(each plot is 1000 m2) for each stand and 240 circular(25 m2) plots for regeneration within the burned and unburned areas,respectively.In each plot,habitat factors were recorded,including crown canopy percentage,forest stratum,herb-layer cover percentage,species,diameter at breast height,tree and regeneration quality,and quantity of seedlings and saplings.Our results showed that bark is an important factor for fire resistance in Hyrcanian forests.The Persian ironwood and European yew has the highest and lowest fire resistance;as broad leave species are more resistant than needle leaf species.Density of regeneration in unburned area was higher than burned area,and statistical analysis showed significant differences for all species between two areas.Fire effects on sapling were different among species which indicates sapling has different resistance to fire.Forest floor fuel,season,stand composition and microclimate have more effects on fire severity while environmental factors,regeneration and management practices shaping future composition stands.  相似文献   

Feed discrimination and selection in self-fed European sea bass Dicentrarchus labrax L.     

M Paspatis  D Maragoudaki  & M Kentouri 《Aquaculture Research》2002,33(7):509-514

Abstract This study was conducted to evaluate feed discrimination and preference of European sea bass Dicentrarchus labrax L., taking into account the effects of feed location, previous feeding experience and light conditions. Fish (63 g) were held in tanks and exposed to a 12L:12D photoperiod and ambient temperature. The following feeding practices were applied in triplicate: three‐choice feeding (self‐ feeding with feeds formulated for carnivorous, herbivorous and omnivorous fish rotated on a weekly basis) and monofeeding (self‐feeding with one of these feeds). After 9 weeks (phase I), fish previously held in monofeeding, were subjected to three‐choice feeding for 2 weeks (phase II). In phase I, fish discriminated between feeds after their rotational displacements and preferred the feed formulated for carnivorous species. This also supported the best growth. Fish used in phase II preferred the same feed. There was no preference for any location within tanks. Feeding was generally diurnal, although in some tests with the feeds for herbivores and omnivores, diurnal and nocturnal feed demands were similar and fewer in number than with the feed formulated for carnivores.  相似文献   

Growth, digestibility and nutrient utilization of rainbow trout (Oncorhynchus mykiss) and European sea bass (Dicentrarchus labrax) juveniles fed different dietary soybean oil levels     

D. Alves Martins  E. Gomes  P. Rema  J. Dias  R.O.A. Ozório  L.M.P. Valente 《Aquaculture International》2006,14(3):285-295

A shortage of marine raw ingredients, such as fish oil, is predicted in the near future. The use of suitable alternative lipid sources, such as vegetable oils, is crucial for sustainable growth of the aquaculture sector. Three isonitrogenous (50% Crude Protein) and isoenergetic (19 kJ g⁻¹) diets, in which fish oil was gradually replaced by soybean oil (0, 25 and 50% of the oil fraction) were tested for 12 weeks, using European sea bass (Dicentrarchus labrax) and rainbow trout (Oncorhynchus mykiss) juveniles. No dietary effects (p>0.05) on growth performance, feed conversion, digestibility or body composition were observed with either species. The results obtained suggest the inclusion of soybean oil up to 50% of the dietary lipid is possible, in diets for sea bass and/or rainbow trout juveniles.  相似文献   

The GnRH systems in the brain and pituitary of normal and hCG treated European silver eels     

O. Kah  S. Dufour  S. Baloche  B. Breton 《Fish physiology and biochemistry》1989,6(5):279-284

The distribution of immunoreactive GnRH was studied in the brain and pituitary gland of normal and human chorionic gonadotrophin (hCG) injected silver eels. It was found that the general organization of GnRH systems in this species is similar to that reported in other teleosts. Cell bodies were present in the olfactory bulbs, ventral telencephalon, periventricular hypothalamus and dorsal tegmentum. No positive perikarya could be detected in the preoptic region. Only scarce fibers were observed in the proximal neurohypophysis. Treatment with hCG does not modify the distribution of GnRH but it increases the density of positive structures, in particular at the level of the pituitary. The results are discussed in relation with the present status of knowledge of the mechanisms underlying the blockage of sexual maturation in the European eel at the silver stage.  相似文献   

Successful storage and transport of eggs of the white-clawed crayfish (Austropotamobius pallipes Lereboullet)     

J.D. Celada  J.M. Carral  J.R. Pérez  M. Sáez-Royuela  C. Muñoz 《Aquaculture International》2002,9(3):269-271

Embryonated eggs of theEuropean native white-clawed crayfish Austropotamobius pallipes Lereboullet weresubjected to three periods of storage usingpolystyrene boxes and, afterwards, artificiallyincubated. At the end of the longest storage(42 days) survival rate was 98.3%, with 65%developed to stage 2 juvenile. Differentstorage periods allowed the staggeredproduction of juvenile batches within a monthperiod. The same containers used for storagewere also suitable for transport.  相似文献   

Effects of dietary l-carnitine supplementation on growth and lipid metabolism in European seabass (Dicentrarchus labrax)   总被引：1，自引：0，他引：1  

J Dias  J Arzel  G Corraze  & J Kaushik 《Aquaculture Research》2001,32(S1):206-215

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Competitive interactions between native and exotic salmonids: a combined field and laboratory demonstration   总被引：4，自引：0，他引：4  

S. Blanchet  G. Loot  G. Grenouillet  S. Brosse 《Ecology of Freshwater Fish》2007,16(2):133-143

Abstract –  We studied the impact of two exotic salmonid species (brook trout, Salvelinus fontinalis and rainbow trout, Oncorhynchus mykiss ) on native brown trout ( Salmo trutta fario ) habitat, growth and survival. Habitat selection and vertical distribution between young-of-the-year of the three species were examined in a stream aquarium under different sympatric and allopatric combinations. In addition, similar species combinations were introduced in a Pyrenean mountain stream (southwest France) in order to extend laboratory results to growth and apparent survival. Both laboratory and field results indicated that rainbow trout significantly affected native brown trout habitat selection and apparent survival. On the contrary, brown trout habitat, growth and apparent survival were hardly affected by brook trout. These results support the idea that rainbow trout negatively influence native brown trout, and that competition could influence the outcome of fish biological invasions in freshwater ecosystems.  相似文献   

Selectivity of flexible size-sorting grid in Mediterranean multispecies trawl fishery     

Nixon Bahamon  Francesc Sardà  Petri Suuronen 《Fisheries Science》2007,73(6):1231-1240

ABSTRACT:   The demersal multispecies trawl fishery in the western Mediterranean Sea has a poor selectivity; large numbers of juvenile fish are caught when using the legislated 40-mm diamond mesh cod end. The selectivity of a flexible sorting grid with 20-mm bar spacing (BS20) installed in front the conventional trawl cod end was investigated. The standard covered cod end method was used. Data was adequate for analyzing the selectivity of European hake Merluccius merluccius , poor cod Trisopterus minutus , greater forkbeard Phycis blennoides and Norway lobster Nephrops norvegicus . The selectivity of the 20-mm sorting grid was compared with the performance of 40-mm diamond (DM40) and square mesh (SM40) cod ends. The effect of a guiding funnel on the performance of the grid (BS20-f) was also explored. Finally, the potential changes in yield per recruit (Y/R) and biomass per recruit (B/R) after implementing a sorting grid were explored. An overall improvement in the 50% selection length ( L ₅₀ ) with all four species was substantial when comparing the BS20 to the DM40. Higher improvement in L ₅₀ s was achieved when the grid was equipped with the guiding funnel. When comparing the performance of the BS20-f to the SM40, there was no marked difference in L ₅₀ s. The Y/R and B/R, however, are substantially higher with BS20-f for poor cod and about the same for European hake. BS20 compared to SM40 achieved lower Y/R and B/R for all four species; the smallest difference was observed for Norway lobster. Further development is required if the sorting grid is to be introduced into commercial fisheries.  相似文献   

Physio-Chemical Characteristics of Seminal Plasma and Development of Media and Methods for the Cryopreservation of European eel Sperm     

J. F. Asturiano  L. Pérez  D. L. Garzón  F. Marco-Jiménez  D. S. Peñaranda  J. S. Vicente  M. Jover 《Fish physiology and biochemistry》2004,30(3-4):283-293

The high sperm density, together with the short spermatozoa swimming time, makes European eel sperm manipulation and assessment for quality difficult. Two diluting media (K15 and K30) previously designed for Japanese eel sperm were tested. After 24 h, European eel sperm showed significant reduction in the percentage of motile spermatozoa after activation and different motility parameters (VAP, angular velocity; VCL, curvilinear velocity; VSL, straight line velocity; BCF, beating cross frequency), concluding that these media are not suitable to preserve the sperm of this species. After a hormonal treatment to induce spermiation, sperm volume, density and motility were recorded at weekly samplings. The variation of the osmolality (325–330 mOsm kg⁻¹), pH (8.4–8.6) and the ionic composition (concentration of Na⁺, K⁺, Mg²⁺ and Ca²⁺) of the seminal plasma were registered. Physio-chemical results were related with sperm quality throughout the treatment, to determine which must be the suitable characteristics of one extender for the sperm of this species, and to find the best conditions to obtain suitable cryopreservation media for European eel sperm. K⁺ concentration increased, while Ca²⁺ and Mg²⁺ concentrations showed a progressive reduction in correlation with the sperm quality improvement. Na⁺ showed a decreasing, but not significant tendency. P1 and P2 freezing media were designed considering the physio-chemical parameters as well as the ionic composition shown by the best quality sperm samples, and then compared with the previously described solutions, TNK and K30. Sperm quality was determined, checking the percentage of motile spermatozoa and motility parameters using computer-assisted sperm analysis (CASA) software. Samples were frozen after dilution (1:5, 1:20, 1:100) in different freezing media supplemented with 10% dimethyl sulfoxide (DMSO). After thawing, samples frozen with low dilution ratio (1:5) in TNK and P1 media showed higher, although not significant, spermatozoa survival (35.5 ± 14.5 and 36.6 ± 6.7%). The addition of l-α-phosphatidylcholine to the media seems to have a positive effect, as reported in the Japanese eel.  相似文献   

Characterization of acetylcholinesterase and its molecular forms in organs of five freshwater teleosts   总被引：1，自引：0，他引：1  

J. Ferenczy  T. Szegletes  T. Bálint  M. Ábrahám  J. Nemcsók 《Fish physiology and biochemistry》1997,16(6):515-529

The activity and molecular forms of acetylcholinesterase (AChE, EC 3.1.1.7) were characterized in the brain, heart, white skeletal muscle and liver of the Siberian sturgeon (Acipenser baeri), European eel (Anguilla anguilla), wels (Silurus glanis), common carp (Cyprinus carpio) and silver carp (Hypophthalmichthys molitrix), belonging in four families. The brain had the highest (between 183.2±10.6 and 1361.2±189.7 mU mg^-1 protein and between 4.7±0.4 and 23.5±2.7 U g^-1 wet tissue) and the liver the lowest (between 25.3±1.9 and 126.5±22.7 mU mg^-1 protein and between 1.0±0.1 and 4.5±0.5 U g^-1 wet tissue) activity in all these fish, with the exception of the wels, where the heart contained the smallest amount of AChE (26.2±7.5 mU mg^-1 protein and 1.2±0.3 U g^-1 wet tissue). The highest tissue AChE activity was found in the carp and lowest in the sturgeon. The solubility properties and molecular forms of AChE in the four tissues were studied by extraction in high-salt medium (1.0 M NaCl) with and without the detergent Triton X-100 (0.5%, v/v). The proportions of detergent-soluble (DS) and salt-soluble (SS) forms of AChE varied considerably from one species to another, but a general tendency could be observed: the proportion of DS AChE was generally higher in the brain (between 70.4±4.1 and 82.5±1.2%) and lower in the heart (between 12.0±2.0 and 51.3±2.3%) and skeletal muscle (between 16.0±2.0 and 64.4±0.7%). Velocity sedimentation centrifugation revealed that most tissues contained the G₄ or A₄ form. Three tissues (brain, heart, and liver) of the Siberian sturgeon contained a relatively high proportion of the G1 form (between 24.3±2.4 and 28.6±4.9%), while the skeletal muscle of the wels contained only the most complex type of AChE, i.e., A₁₂. Amongst the tissues studied, the brain and liver mostly contained amphiphilic globular forms of the G₄ type, while the heart and skeletal muscle were rich in asymmetric forms (A₄ and A₁₂). It was concluded that the differences revealed in the activities of AChE and in the distribution of its molecular forms may be connected with the variation in behavioral habits (feeding and swimming patterns), and the developmental stage of the nervous system.  相似文献