Biotic passage through the Panama Canal,with particular reference to fishes

The effectiveness of the Gatun Lake fresh-water barrier to fish migration of the Panama Canal was examined, based on literature records and recent collections. Six species have migrated to the Pacific and three to the Atlantic Oceans. New records include: Hypleurochilus aequipinnis, Barbulifer ceuthoecus and Oostethus lineatus of Atlantic origin, and Gnathanodon, speciosus of Pacific origin. The majority of Atlantic migrants are known in the Pacific only from the Miraflores Third Lock, a unique ectogenic meromictic lake attached to the Pacific entrance of the canal. The hydrography and biota (including Atlantic algal and crustacean species previously unknown as canal migrants) of the lake are discussed. It is presumed that certain fish migrants transited the canal by associating with fouling material on the underside of ships. The euryhaline species, H. aequipinnis, Lupinoblennius dispar, Lophogobius cyprinoides and Omobranchus punctatus survived in freshwater (0.0‰S) for periods longer than réquired for ship transit of the canal (ca. 8h). The stenohaline migrant Gobiosoma nudum died after 2 h in freshwater, but survived more than 50 h at 2.5‰S. Plans to increase Panama Canal ship transits through the pumping of seawater into Gatún Lake might remove the biological barrier and allow the migration of euryhaline and stenohaline species. We find those plans unwise, and the potential consequences dangerous.     

Context-dependent genetic benefits of extra-pair mate choice in a socially monogamous passerine

Extra-pair paternity is common in socially monogamous passerines; however, despite considerable research attention, consistent differences in fitness between within-pair offspring (WPO) and extra-pair offspring (EPO) have not been demonstrated. Recent evidence indicates that differences between maternal half-siblings may depend on environmental conditions, but it is unclear whether the influence of paternal genetic contribution should be most apparent under comparatively poor or favourable conditions. We compared phenotypic characteristics of WPO and EPO in 30 mixed-paternity broods of the tree swallow (Tachycineta bicolor) in relation to experimentally increased nest temperature (n = 13 heated nests; 17 control nests) and natural abundance of haematophagous parasites (Protocalliphora spp.). This allowed us to test the hypothesis that genetic benefits of extra-pair mating are environment dependent. EPO grew their ninth primary feathers faster than WPO regardless of nest temperature or parasite load and had significantly longer ninth primary feathers at fledging when parasite abundance was low, and when they were positioned early in the hatching sequence relative to WPO. In contrast, WPO under similar conditions did not differ from EPO in any phenotypic trait measured. These results indicate that the fitness benefits of extra-pair mating are likely to be context dependent, and that genetic effects on some phenotypic traits may be more apparent when conditions are relatively favourable.     

The bottlenose dolphin community of Doubtful Sound features a large proportion of long-lasting associations

More than 12 studies of different bottlenose dolphin populations, spanning from tropical to cold temperate waters, have shown that the species typically lives in societies in which relationships among individuals are predominantly fluid. In all cases dolphins lived in small groups characterised by fluid and dynamic interactions and some degree of dispersal from the natal group by both sexes. We describe a small, closed population of bottlenose dolphins living at the southern extreme of the species' range. Individuals live in large, mixed-sex groups in which no permanent emigration/immigration has been observed over the past 7 years. All members within the community are relatively closely associated (average half-weight index>0.4). Both male–male and female–female networks of preferred associates are present, as are long-lasting associations across sexes. The community structure is temporally stable, compared to other bottlenose dolphin populations, and constant companionship seems to be prevalent in the temporal association pattern. Such high degrees of stability are unprecedented in studies of bottlenose dolphins and may be related to the ecological constraints of Doubtful Sound. Fjords are low-productivity systems in which survival may easily require a greater level of co-operation, and hence group stability. These conditions are also present in other cetacean populations forming stable groups. We therefore hypothesise that ecological constraints are important factors shaping social interactions within cetacean societies.Communicated by D. Watts     

Experimental evidence for food limitation and sex-specific strategies of American kestrels (<Emphasis Type="Italic">Falco sparverius</Emphasis>) provisioning offspring

For birds with altricial young, the brood-rearing period is one of the most energetically expensive periods in their lives and may be the bottleneck for fitness. Because parents are expected to be prudent in allocating resources between reproduction and self-maintenance, food supply should be an important factor determining reproductive decisions during brood rearing. Parents with abundant food are expected to have enhanced fitness because they are able to reduce their work rates and increase their own survival chances, because their offspring may be of higher quality, or some combination of these. However, few studies have simultaneously documented all of these variables in a single investigation. We performed a food supplementation experiment to test how food supply influenced provisioning decisions by parent American kestrels (Falco sparverius). Female kestrels showed a strong response to extra food and reduced their provisioning rates. As a result, supplemented females had higher return rates than control females, suggesting significant effects of food on female survival. Because females used extra food to increase their fitness, our results suggest that kestrels raising offspring are limited by food. Male kestrels whose nests were supplemented also responded to extra food by reducing provisioning, but to a much lesser extent than their mates. Male parents did not appear to benefit from supplementation, as their return rates were similar to control males. The total amount of food received on a daily basis by nestlings was similar between supplemented and control nests. Supplemented offspring therefore did not fledge in better condition or have higher survival rates than control nestlings; the only significant factor consistently affecting offspring condition and survival was weather.     

Toxic Substances in the Atmospheric Environment Discussion

The Critical Review on Toxic Substances in the Atmospheric Environment was presented by Bernard D. Goldstein at the 76th Annual Meeting of the Air Pollution Control Association in Atlanta, Georgia. Dr. Goldstein summarized his paper, which had been published in the May 1983 issue of JAPCA. Prepared discussions presented at the Critical Review Session are reproduced here. In addition, comments made from the floor and through the mails have been formalized and are published along with closing remarks by Dr. Goldstein. Dr. Paul J. Lioy served as Moderator for the 1983 Critical Review Session.     

Predicting Sample Source Location from Soil Analysis Using Neural Networks

A system combining a national soils database with a neural network was developed for prediction of source location for soil samples. The neural network was trained to predict environmental characteristics, which can be of crucial importance to investigating officers in a police operation or to environmental agencies attempting to locate the source of a pollutant. When coupled with maps of environmental conditions and a generalized opinion pool approach, the system was used to produce weighted maps of source location. The system was capable of reducing search areas of a sample source to less than 0.1% of the total area.     

“The End of the Ice Age?”: Disappearing World Heritage and the Climate Change Communication Imperative

Rapid environmental change in vulnerable destinations has stimulated a new form of travel termed “last chance tourism” (LCT). Studies have examined the risks of LCT, while leaving potential opportunities within this new tourism market largely underexplored. Results of survey (n?=?399) research in Jasper National Park, Canada reveal that a LCT motivation influences decisions to visit this iconic Canadian destination, and suggest that this motivation is linked to a desire to learn about the impacts of climate change on the Athabasca Glacier. Findings suggest there may be short to medium term opportunities associated with LCT, including promoting climate change ambassadorship through management interventions. This paper discusses a range of possible education, interpretive, and outreach activities that might be employed at LCT destinations. It outlines the relative merits (or what we refer to as “uneasy benefits”) of promoting the glacier and other LCT destinations within a protected areas management and climate change adaptation context.     

Agricultural causes of desertification risk in Minqin, China

This study uses statistical modeling techniques to develop a desertification risk index (RI) for Minqin County, Gansu Province, China. Twenty socio-economic factors were selected and compared with the RI results to explore the spatial and temporal variability of desertification risk in the study area and to identify possible local driving forces behind desertification risk. The explanatory factors were different in 1988, 1992 and 1997, possibly reflecting the role of temporal variation as a contributor to desertification. The average number of sheep per-household was found to be an important indicator of change in desertification risk, while changes in ridge crop planting area explained the distribution of the rate of change in desertification risk in 1988-1992. The results suggests that the RI was useful in expanding the understanding of spatial temporal desertification issues in Minqin County, as well as identifying a current set of agricultural activities related to desertification risk. Further, given the limited nature of consistent data and observations for the area, development of the RI also served to establish a baseline for future investigations into desertification change and the risks such change might pose for the region.     

Prediction of fish bioconcentration factors of nonpolar organic pollutants based on molecular connectivity indices.

The relationship between bioconcentration factors and molecular connectivity indices was investigated. A regression model was developed using 80 measured BCFs of nonpolar organic pollutants. The five topological parameters used were 1 chi, 2 chi, 3 chi c, 0 chi v and 2 chi v. Modified jackknife tests were applied to examine the robustness of the model by repeatedly removing a set of or a class of compounds from the database. The model was compared with one using Kow as an independent parameter. The mean absolute errors for the 80 compounds studied were 0.288 and 0.302 log-unit for the two models, respectively.