Reproductive performance of cultured brown trout (Salmo trutta L.) in Chile

Data on reproductive traits in a cultured population of brown trout (Salmo trutta L.) in southern Chile were collected over three consecutive reproductive seasons: 1999, 2000 and 2001, corresponding to the first (at 3 years), second and third spawnings in females. Data were collected from individual females (n=238, 273 and 169 respectively). The reproductive season lasted mainly from June to August. The peak (July) tended to increase with each season (55.46%, 62.27% and 80.81% of total spawning fish respectively). Female body weight (470.8±102.5, 735.0±150 and 1263.9±263.4 g), total fecundity (1182±344, 1904±595 and 2744±605) and egg diameter (4.64±0.11, 4.67±0.27 and 5.24±0.12 mm) increased significantly (P<0.01) over successive reproductive seasons, particularly between the second and third spawnings. Relative fecundity, on the other hand, decreased significantly with each season (3577±471, 2591±900 and 2181±360). Following analysis of the variables over the three seasons, the correlation pattern of female body weight with total fecundity (r=0.91, n=458; P<0.001) and relative fecundity (r=?034, n=451; P<0.001) proved similar to that described in other salmonid females. Fertilization rate and survival to the eyed egg stage were also positively correlated (r=0.73, n=453; P<0.001). The systematically high values obtained for these latter variables over the seasons evaluated (consistently above 90%) are clearly greater than those we registered in other species of salmonids bred in Chile under similar conditions and suggest highly efficient biological variables that determine the gamete fertilization of this species. The brown trout is, therefore, an interesting potential aquaculture resource in Chile.     

Binding and bioactivity of insulin in primary cultures of carp (Cyprinus carpio) hepatocytes

Isolated carp hepatocytes cultured in serum-free, chemically defined medium were used to investigate within the same cell preparation characteristics of the binding of insulin as well as effects of insulin on cellular metabolism. The binding of human [¹²⁵I]-insulin to carp hepatocytes was studied in kinetic, saturation and displacement experiments. A dependency of insulin binding on the collagenase used for cell isolation was demonstrated. Insulin binding decreased during the first 12h of culture but remained constant during the following 12h. The kinetic experiments revealed that [¹²⁵I]-insulin binding reached a steady state within 20–30 min of incubation. The mathematical analysis of the saturation experiments demonstrated the existence of two populations of binding sites, one with high affinity (K_d1 = 5.5 pM) and low capacity (B_max1 = 0.14 fmol/mg protein or 77 binding sites/cell) and one with low affinity (K_d2 = 2.4 nM) and high capacity (B_max2 = 17.6 fmol/mg protein or 9623 binding sites/cell). In competition experiments, 312 pM [¹²⁵I]-insulin was displaced by cold insulin, IGF-I and IGF-II with IC₅₀ values of 2.2, 7.9 and 20.3 nM, respectively. Glucagon was without effect. Binding of insulin to carp hepatocytes resulted in a significant reduction of glucose release and a significant increase of protein synthesis as of de novo fatty acid synthesis. dedicated to Prof. Dr. W. Hanke on the occasion of his 65^th birthday.     

Diel Foraging Behavior of American White Pelicans Pelecanus erythrorhynchos on Experimental Aquaculture Ponds

Videography and night vision equipment were used to observe the diurnal and nocturnal activities of American white pelicans Pelecanus erythrorhynchos ( N =6) foraging on three experimental (0.04 ha) channel catfish ( Ictalurus punctatus ) aquaculture ponds in March 2001. Captive pelicans spent most time foraging per hour from 1700 through 2300 h (CST). No foraging was observed from 0700 through 0800 h. Fish captures per hour were greatest from 1700 through 1900 h. On average, captive pelicans ( N = 5) consumed 1.0 ± 0.2 kg of catfish per bird per day during the 10-d foraging trial. This consumption corresponds with an average intake of over 60,000 kJ of energy per bird during the trial. Relative to morning hours, the average number of bill dips per min was greater during afternoon foraging bouts. Fish captures per bill dip, however, did not differ among trial hours. Thus, pelicans were observed to increase foraging effort subsequent to 1500 h and thereby consumed 224 to 532 catfish (average = 313 ± 74 fish; N = 4) during the 10-d foraging trial in ponds stocked with approximately 74,000 catfish/ha.     

Stability of bacterial leaf spot resistance in peach regenerants under in vitro,greenhouse and field conditions

Summary Phenotypic stability of bacterial leaf spot resistance in peach (Prunus persica (L.) Batsch) regenerants, either selected at the cellular level for insensitivity to a toxic culture filtrate of Xanthomonas campestris pv. pruni or screened at the whole plant level for resistance to X. campestris pv. pruni, was investigated. A detached-leaf bioassay was used to evaluate the original regenerants again after three years in the greenhouse and also after a two to three year cycle of tissue culture propagation. Peach trees derived through micropropagation from the original regenerants were also evaluated after one to three years growth in the field. Although leaf spot resistance was retained in some regenerants over time in the greenhouse, following in vitro propagation, and under field conditions, resistance was either lost or not expressed in others. Regenerants # 19-1 and #156-6, derived from embryo callus of bacterial spot susceptible Sunhigh, were significantly more resistant than Sunhigh. High levels of resistance were exhibited in greenhouse plants and field-grown trees of regenerant #122-1, derived from embryo callus of moderately resistant Redhaven. This research provides additional evidence that selecting or screening for somaclonal variants with disease resistance is a feasible approach to obtaining peach trees with increased levels of bacterial spot resistance.Abbreviations TC Tissue-Cultured - TF Toxic culture Filtrate     

Mushroom picking does not impair future harvests - results of a long-term study in Switzerland

Forest fungi not only have important functions within the forest ecosystem, but picking their fruit bodies is also a popular past time, as well as a source of income in many developing and developed countries. The expansion of commercial harvesting in many parts of the world has led to widespread concern about overharvesting and possible damage to fungal resources. In 1975, we started a field research project to investigate the effects of mushroom picking on fruit body occurrence. The three treatments applied were the harvesting techniques picking and cutting, and the concomitant trampling of the forest floor. The results reveal that, contrary to expectations, long-term and systematic harvesting reduces neither the future yields of fruit bodies nor the species richness of wild forest fungi, irrespective of whether the harvesting technique was picking or cutting. Forest floor trampling does, however, reduce fruit body numbers, but our data show no evidence that trampling damaged the soil mycelia in the studied time period.     

Acute effects of wood-pulp on sockeye salmon (Oncorhynchus Nerka)

Freshwater suspensions of pulp fiber in concentrations exceeding 1000 ppm at 15°C are acutely lethal to sockeye salmon fingerlings. Limited adaptation of such fish to fiber is possible but injury, at least in the short term, is irreversible. The acute lethality of various toxicants associated with industrial pulps is synergistically enhanced by the presence of fiber, and pulp storage up to 158 days at 15°C had no significant effect on the acute lethality. Highly purified fibers are less toxic in fresh than in sea water. The sensitivity to fiber of fish from two sources did not differ significantly.     

Habitat use of the three-toed woodpecker in central Europe during the breeding period

Considerable differences observed in the home-range size of individual three-toed woodpeckers (Picoides tridactylus) may be linked to variation in resource availability. We used radio-telemetry to test this hypothesis in an alpine mountain forest in southeastern Germany between 1994 and 2000. Stepwise backward multiple-regression showed that adaptive kernel home-range size using 95% use distribution (n=24 woodpeckers) was positively related to forest extent and tree-species diversity. Conversely, we found smaller home ranges with increasing density of potential cavity trees, and with increasing dbh-range of trees at breast height. The habitat variables shown to effect home range selection were attributes of mature boreal forests. This implied that maintaining a boreal-like habitat (i.e. spruce-dominated autochthonous forests including their natural disturbance regime) would be the best option for successful conservation of the alpine subspecies of the three-toed woodpecker.