The effect of acoustic harassment devices on harbour porpoises (Phocoena phocoena) in the Bay of Fundy, Canada

Many salmon aquaculture sites in the Bay of Fundy employ acoustic harassment devices (AHDs) to deter seals from approaching fish pens. These devices may also exclude harbour porpoises (Phocoena phocoena) from important habitat. To determine the effects of AHDs on harbour porpoises an AHD was deployed experimentally in the Bay of Fundy, Canada. Relative porpoise abundance (visual scans) and porpoise movements (tracked by theodolite) were recorded for separate, daily, 2-h periods in the vicinity of either an active (n=9) or inactive (n=7) AHD. Fewer porpoises were sighted during active periods (0.22±0.44, mean±SD ) than inactive periods (2.91±1.29; P<0.05). The mean closest observed approach of porpoises to the AHD during active periods (991±302 m) was significantly greater than during inactive periods (364±261 m; P<0.01). Porpoise density was therefore reduced in the vicinity of active an AHD. These results should be considered before AHDs are deployed in porpoise habitat.     

Linking colonies to fisheries: Spatio-temporal overlap between common murres (Uria aalge) from Tatoosh Island and coastal gillnet fisheries in the Pacific Northwest, USA

The population-level impact of seabird bycatch is difficult to assess because colony-of-origin is often unknown. As an alternative and complementary approach to ship-derived observations, we assessed the relative potential for bycatch of a known seabird population by quantifying spatio-temporal overlap with local fisheries. Common murres (Uria aalge) have been reported as the most abundant seabird inadvertently caught in Washington and British Columbia coastal gillnet fisheries. In 1999-2001, we tracked 48 common murres from Tatoosh Island, the closest colony to the fisheries, during post-breeding. Using capture-mark-recapture models, we estimated weekly murre movement probabilities to/from three strata (offshore of, centered around, and inshore of Tatoosh Island). Based on movement probabilities and population size, we projected strata- and week-specific murre abundance. We created an index of overlap by calculating the product of murre abundance × gillnet fishing effort as a function of strata and time. The majority of murres (80%) moved inshore, where fishing effort was consistently the highest, suggesting that up to 4000 Tatoosh murres were vulnerable to bycatch. Index scores in the inshore stratum were 5-25 times higher relative to the offshore and Tatoosh strata, respectively. Overlap was sensitive to phenology, as index scores increased by 50% when dispersal was shifted four weeks earlier, while a two weeks delay decreased scores by 20%. Until the long-term impact of cumulative mortality in gillnet fisheries is determined, we believe a precautionary approach is warranted in the inshore stratum where the potential for bycatch was highest. We advocate the use of visible netting in inshore fisheries, a proven solution that reduces murre bycatch while maintaining fishing efficiency.     

Bycatches of common guillemot (Uria aalge) in the Baltic Sea gillnet fishery

Bycatch of common guillemots (Uria aalge) appears to be the single most serious threat to the population, and the proportion of recoveries of ringed birds in fishing gear, compared with other finding circumstances, has significantly increased during a 28 year period (P<0.01). Out of 1952 ringed common guillemots reported found between 1972 and 1999 in the Baltic Sea, 980 (50.2%) were caught in fishing gear. The bycatch in set gillnets for cod (Gadus morhua) constituted 22.3%, drift gillnets for salmon (Salmo salar) 65.5%, and other fishing gear 12.2%. The proportion of recoveries in cod gillnets has significantly increased during the study period (P<0.05), while no clear trend was observed in the recoveries in salmon gillnets. The Swedish fishing effort follows a similar pattern for cod but has decreased for salmon. The observed increased use of cod gillnets in the Baltic Sea may have contributed to the observed decrease in adult survival rate, and we provide two different estimates suggesting that significant proportions of the guillemot population are caught annually in the Baltic Sea gillnet fishery. We suggest several available techniques to reduce bycatch in the Baltic Sea fishery.     

Measurement, management and mitigation of operational interactions between the South Australian Sardine Fishery and short-beaked common dolphins (Delphinus delphis)

This study arose from recommendations given in response to a legislated ecological assessment of the South Australian Sardine Fishery in 2004, urging it to: (i) attempt to mitigate operational interactions with marine mammals if excessive levels were detected; and (ii) improve the accuracy of their reporting of these events.An initial observer program revealed high rates of encirclement and mortality (1.78 and 0.39 dolphins per net-set, respectively) of short-beaked common dolphins (Delphinus delphis). This equated to an estimate of 1728 encirclements and 377 mortalities across the entire fleet over the same period. The average time taken for fishers to respond to encirclements was 135.93 ± 3.72 min and 21.3% of encircled animals subsequently died. During that time, fishers only reported 3.6% of encirclements and 1.9% of mortalities recorded by observers.A code of practice (CoP) was subsequently introduced aimed at mitigating operational interactions. A second observer program revealed a significant reductions in the observed rates of dolphin encirclement (0.22; down 87.3%) and mortality (0.01; down 97.1%) with an estimate of 169 and eight, respectively. The average time taken for fishers to respond to dolphin encirclements also reduced to 16.33 ± 4.67 min (down 76.9%) and the proportion of encircled animals that subsequently died reduced to 5.0%. Agreement between industry reports and observer records improved, with the fishery reporting 57.9% and 58.9% of the rate of encirclements and mortalities, respectively, recorded by observers.A number of avoidance and release strategies in the CoP may have been responsible for these improvements. In particular, fishers were required to delay or relocate their activities if dolphins were observed prior to fishing and to release encircled dolphins immediately or abort the fishing event if release procedures were unsuccessful. Future improvements to the CoP include: (i) improved response times when an encircled dolphin is detected; (ii) better use of behavioural cues for deciding when to abort a net-set; (iii) ceasing fishing during rough weather; and (iv) continuing to increase reporting accuracy by fishers. It is also recommended that the abundance, movements and boundaries of the common dolphin population in the region be determined, so that the impact of fishing activities on their status can be established.     

Conservation implications of the genetic and ecological distinction of Tursiops truncatus ecotypes in the Gulf of California

The demand for live bottlenose dolphins for commercial use is growing in Mexico, making the need for stock assessment and management ever more essential given their protected status. Tursiops truncatus is known to exhibit high levels of phenotypic polymorphisms. In the Gulf of California (GC), coastal and offshore ecotypes have been identified based on morphological, behavioral and ecological evidence, including different prey and habitat preferences. However, the extent to which this ecological and phenotypic variation is genetically correlated is unknown. Here we assess this correlation in GC bottlenose dolphins classified as coastal or offshore based on habitat, morphological and trophic evidence. Significant (p < 0.0001) haplotype heterogeneity (exact test) and genetic differentiation (F_ST = 0.069) were found in the mitochondrial control region, indicating some reproductive isolation between ecotypes. As elsewhere, coastal dolphins were less diverse than offshore. Phylogenetic analyses revealed paraphyletic coastal and offshore lineages and no evidence of lineage sorting, possibly due to recent isolation or gene flow. This is the first time that genetic, morphological and stable isotope evidence has been used to recognize ecotypes as different stocks for management purposes in bottlenose dolphins. Our results indicate that diversifying forces are shaping their phenotypic and genetic variation in the GC. Management and conservation efforts in this strategic region should aim to preserve these forces.     

Accumulation of specific flavonoids in soybean (Glycine max (L.) Merr.) as a function of the early tripartite symbiosis with arbuscular mycorrhizal fungi and Bradyrhizobium japonicum (Kirchner) Jordan

This study is the first report assessing the effect of soil inoculation on the signalling interaction of Bradyrhizobium japonicum, arbuscular mycorrhizal fungi (AMF) and soybean plants throughout the early stages of colonisation that lead to the tripartite symbiosis. In a study using soil disturbance to produce contrasting indigenous AMF treatments, the flavonoids daidzein, genistein and coumestrol were identified as possible signals for regulating the establishment of the tripartite symbiosis. However, it was unclear whether soil disturbance induced changes in flavonoid root accumulation other than through changing the potential for AMF colonization. In this study, soil treatments comprising all possible combinations of AMF and B. japonicum were established to test whether (1) modifications in root flavonoid accumulation depend on the potential for AMF colonization, and (2) synthesis and accumulation of flavonoids in the roots change over time as a function of the early plant-microbial interactions that lead to the tripartite symbiosis. The study was comprised of two phases. First, maize was grown over 3-week periods to promote the development of the AM fungus Glomus clarum. Second, the interaction between soybean, G. clarum and B. japonicum was evaluated at 6, 10, 14 and 40 days after plant emergence. Root colonization by G. clarum had a positive effect on nodulation 14 days after emergence, producing, 30% more nodules which were 40% heavier than those on roots solely inoculated with B. japonicum. The tripartite symbiosis resulted in 23% more N₂ being fixed than did the simpler symbiosis between soybean and B. japonicum. The presence of both symbionts changed accumulation of flavonoids in roots. Daidzein and coumestrol increased with plant growth. However, development of the tripartite symbiosis caused a decrease in coumestrol; accumulation of daidzein, the most abundant flavonoid, was reduced in the presence of AMF.     

Interactions between the arbuscular mycorrhizal fungus Glomus intraradices and the plant growth promoting rhizobacteria Paenibacillus polymyxa and P. macerans in the mycorrhizosphere of Cucumis sativus

Interactions between the arbuscular mycorrhizal (AM) fungus Glomus intraradices and bacteria from the genus Paenibacillus (P. macerans and P. polymyxa) were examined in a greenhouse pot experiment with Cucumis sativus with and without organic matter amendment (wheat bran). P. polymyxa markedly suppressed AM fungus root colonization irrespective of wheat bran amendment, whereas P. macerans only suppressed AM fungus root colonization in combination with wheat bran amendment. Dual inoculation with P. macerans and G. intraradices in combination with wheat bran amendment also caused severe plant growth suppression. Inoculation with G. intraradices was associated with increased levels of dehydrogenase activity and available P in the growth substrate suggesting that mycorrhiza formation accelerated the decomposition of organic matter resulting in mobilization of phosphorus. Inoculation with both Paenibacillus species increased all measured microbial fatty acid biomarkers in the cucumber rhizosphere, except for the AM fungus biomarker 16:1ω5, which was reduced, though not significantly. Similarly, inoculation with G. intraradices increased all measured microbial fatty acid biomarkers in the cucumber rhizosphere, except for the Gram-positive bacteria biomarker 15:0 anteiso, which was overall decreased by G. intraradices inoculation. In combination with wheat bran amendment G. intraradices inoculation caused a 39% reduction in the amount of 15:0 anteiso in the treatment with P. polymyxa, suggesting that G. intraradices suppressed P. polymyxa in this treatment. In conclusion, plant growth promoting species of Paenibacillus may have suppressive effects of AM fungi and plant growth, especially in combination with organic matter amendment. The use of an inert plant growth media in the present study allowed us to study rhizosphere microbial interactions in a relative simple substrate with limited interference from other soil biota. However, the results obtained in the present work mainly show potential interactions and should not be directly extrapolated to a soil situation.     

High genetic diversity and heterogeneous parasite load in the earthworm Lumbricus terrestris on a German meadow

In parasite-host dynamics, parasites exert frequency-dependent selection on their hosts by favouring rare alleles that may confer resistance against infection. Therefore host populations that suffer strong parasite stress should maintain higher levels of genetic variability. We studied the Lumbricus terrestris-Monocystis sp. host-parasite system at a microgeographical scale. Using three polymorphic microsatellite loci on one large earthworm population sampled at 26 different sites (281 genotypes), we tested the relationship between parasite load and genetic variation in natural samples of the common earthworm L. terrestris. Our analysis yielded the following: (1) parasite load varied significantly across sites in this population; (2) there was no consistent evidence for heterozygote deficiency (observed heterozygosities ranged between 0.74 and 0.87), indicating a low level of inbreeding; (3) there was no significant genetic structuring among sample sites; (4) we could not identify a significant association between parasite load and population genetic diversity; (5) there was considerable population differentiation (15.17%) between our German samples and a Canadian L. terrestris reference population. Our study provides insight into the population genetics of one of the most economically important soil organisms on a microgeographic scale.     

Differences between strains of rhizobium trifolii in ability to colonize soil and plant roots in the absence of their specific host plants

Evidence is presented of strain differences within Rhizobium trifolii in ability to colonize soil surrounding common pasture species, both legume and non-legume, in problem sandy soils in Western Australia. R. lupini and R. trifolii are shown to spread better than R. meliloti in these soils.     

Comparison of g23 gene sequence diversity between Novosphingobium and Sphingomonas phages and phage communities in the floodwater of a Japanese paddy field

Our previous study indicated that the diversity of the major capsid gene (g23) of T4-type bacteriophages (phages) of Novosphingobium and Sphingomonas strains isolated from the floodwater of a Japanese paddy field is comparable to those of the clones obtained from other Japanese paddy fields. For more strict comparison of the diversity, this study examined g23 sequences between Novosphingobium and Sphingomonas phages and phage communities in the identical floodwater of a Japanese paddy field. The clones were obtained by applying g23-specific primers to DNA extracted from the floodwaters. Many 23 clones in the floodwater were grouped into the same clusters of Paddy Groups I-VI with g23 genes of Novosphingobium/Sphingomonas phages with some clones belonging to an additional cluster. In addition, the remaining clones belonged to the clusters of marine clones and T4-type enterophages. These findings indicate that the g23 genes in the floodwater are more diversified than those of Novosphingobium/Sphingomonas phages including g23 genes closely related to the genes of enterophages and marine origins.     

The size and status of the population of southern sea lions Otaria flavescens in the Falkland Islands

Pup production of southern sea lions in the Falkland Islands was estimated to be 80,550 (total population ca. 380,000) in 1937, but by 1965 it had fallen to around 6000; a 93% reduction in under 30 years. We describe the results of an aerial survey of part of the breeding population in 1990 and comprehensive ground counts of the entire population in 1995 and 2003. Results indicate that the decline continued. In 1995, 63 breeding and 42 non-breeding groups were found. Pup production was estimated at 2034 pups; less than 2.7% of the 1930s estimate. All known and potential sites were revisited in 2003. 2747 pups were counted at 68 breeding sites, seven of which were new since 1995. Results indicate that between 1965 and 1990 the population reached a minimum of less than 1.5% of the 1937 population. Since then, pup production has increased at a rate of 8.5% p.a. between 1990 and 1995 and at 3.8% p.a. between 1995 and 2003.The Falklands' trajectory is similar to that of the adjacent Argentinian population. The causes of these declines are not clear. Around 44,000 sea lions were killed in the Falklands between 1935 and 1962, more than 500,000 were taken in Argentina in the same period. We present the results of a simple population model which suggests that, if sea lions migrated between the two areas, the combined hunt may explain the initial decline in the Falklands population. However, the continued decline after 1965 is as yet unexplained.     

Effects of earthworm density on growth, development, and reproduction in Lumbricus rubellus (Hoffm.) and possible consequences for the intrinsic rate of population increase

In this paper, the influence of earthworm density is assessed on the life-history parameters: growth, development, reproduction, and survival of Lumbricus rubellus (Hoffm.). Density ranges from two to nine earthworms in 1-l containers, corresponding to field densities of 300-1350 earthworms m⁻². Earthworms were kept under optimal laboratory conditions, with a surplus of food. The results show that at high earthworm density, individual growth is retarded, maturation delayed and cocoon production decreased, even when food is optimal. The integration of these results into a Dynamic Energy Budget model suggests that the food intake of individual earthworms is lower at the higher tested densities. This lower food intake is most probably driven by competition for space at the higher densities. The lower food intake results in a lower intrinsic rate of population increase which is negative at the highest tested density.     

Differences in the reproductive success and survival of the rufous treecreeper (Climacteris rufa) between a fragmented and unfragmented landscape

The rufous treecreeper (Climacteris rufa) has declined in abundance in the agricultural regions of southwestern Australia. The patterns of decline are well documented, but the processes that threaten population persistence are poorly understood. I compared the reproductive success and survival of the treecreeper between three sites in an unfragmented landscape and four remnant categories (large, small, grazed and ungrazed) in a fragmented, agricultural landscape. Nest success and annual productivity were significantly higher in the unfragmented landscape, but varied between sites and remnant categories within landscapes. Nest success was lowest in grazed remnants and annual productivity was positively associated with territory size in the fragmented landscape. Fledgling survival rates did not differ between landscapes, but there was a trend for juvenile survival rates to be higher in the unfragmented landscape. I used artificial nests to compare relative predation rates between landscapes, and provisioning rates and prey biomass brought to nestlings to assess differences in food availability. There were no landscape differences in predation rates, but provisioning rates to nestlings and total prey biomass were significantly lower in the fragmented landscape. Mean habitat quality was also lower in the fragmented landscape, although it differed between remnant categories. Reduced reproductive success, juvenile survival, food availability and habitat quality may threaten the viability of the rufous treecreeper population living in the fragmented landscape. Limiting the modification of remaining habitat (e.g. removing stock grazing) and improving habitat quality are required to assist in the conservation of this species.     

Reconciling the dichotomy between single species and ecosystem conservation: black kites (Milvus migrans) and eutrophication in pre-Alpine lakes

In recent times there has been a growing dichotomy between preservation of single species and broader, ecosystem-based approaches to conservation. Freshwater habitats are among the most highly human-impacted ecosystems. We used a long-term data set on black kites (Milvus migrans), a threatened raptor dependent on aquatic habitats, to explore ways to reconcile single species and biodiversity-driven approaches to conservation. In the pre-Alpine lakes of northern Italy, black kite populations showed medium-low density, extremely low breeding success and widespread declines. Spatio-temporal variations showed density and breeding success to be positively related to ecosystem productivity (as estimated by phosphorus concentrations in lakes), availability of aquatic habitats and grassland, and to be negatively related to extent of farmland and fish harvest by professional fishermen. Fish species richness, used as a surrogate of biodiversity, was highest in one oligotrophic lake, but on average increased with increasing ecosystem productivity (i.e. lake eutrophication). Given expected future declines in ecosystem productivity, kite conservation will be helped by enhancing populations of alternative prey in terrestrial habitats (e.g. through incentives for grassland), and higher regulation of fish harvest. On the other hand, ecosystem management may profit from the use of black kites or other aerial piscivores as indicators of biodiversity and of diffuse ecosystem stress, such as sustainability of fishing practices.     

Spatial association as an indicator of the potential for future interactions between wind energy developments and golden eagles Aquila chrysaetos in Scotland

Despite their environmental benefits in generating electricity without emission of ‘greenhouse’ gases, wind farms have attracted controversy with regard to their impacts on birds, especially golden eagles Aquila chrysaetos. Evidence from USA studies suggest eagle fatalities through collision with turbines may be the main potential impact whereas for breeding eagles in Scotland, displacement from wind farm areas (indirect habitat loss) may be the primary impact. In this study, we examined the co-occurrence potential for golden eagles and wind farms in Scotland by documenting the spatial association between wind farm proposals and breeding eagle territories and areas potentially suitable for non-breeding eagles. Although there were records for over 500 wind farm proposals at various stages of development, relatively few coincided with eagle territories (ca. 4% of territories had a proposal within 3 km of territory centre). Similarly, only 2% of habitat predicted to be suitable for non-breeding eagles overlapped with proposed or installed wind farm areas. Moreover, estimates of the potential for electricity generation from all wind farm proposals, with respect to government targets for renewable energy supplies, suggested most proposals were unlikely to be constructed. We conclude that in comparison with other constraints on Scotland’s golden eagles, notably persecution, wind farms should not represent a serious concern if best practice in planning their location and minimising their impact are maintained. Potential future regional pressures on breeding eagles from wind farms are highlighted, however, and uncertainty of impact with respect to displacement or collision fatalities requires continued scrutiny.     

Relationship between population size and genetic diversity in endangered populations of the European bullhead (Cottus gobio): implications for conservation

This study investigated the relationship between the current size of endangered bullhead (Cottus gobio) populations and microsatellite genetic variability. Additionally, the microsatellite data were used to evaluate whether a genetic test for population bottlenecks was able to provide evidence of recent severe population declines. Finally, our results were used to develop conservation priorities and measures. Population size appears to be a crucial parameter in determining the amount of genetic diversity that can be preserved in bullheads, since a significant positive correlation was observed between both variables. Furthermore, in some populations we were able to detect genetic signatures of the documented decline in population size. We suggest that the most immediate goal for bullhead conservation should be to increase the size and the range of the populations, and in doing so minimise or even reverse further genetic erosion. Potential management actions like habitat quality improvement, reduction of river fragmentation and supplementation programmes (translocation, supportive breeding) are discussed.     

Discrepancies between ergosterol and the phospholipid fatty acid 18:2ω6,9 as biomarkers for fungi in boreal forest soils

Ergosterol and the phospholipid fatty acid (PLFA) 18:2ω6,9 are frequently used as fungal biomarkers in studies on soils, and in accordance with the ideal for biomarkers of microorganisms they are thought to turn over rapidly after cell death and lysis. These biomarkers should also show the same patterns and responses to perturbations of the studied system. Here, I report strong correlations, in natural boreal forests of contrasting fertility, between free ergosterol and PLFA 18:2ω6,9 (r=0.821, P=0.007, n=9). Surprisingly, ergosterol, but not PLFA 18:2ω6,9, appears non-responsive to both large-scale tree girdling, which interrupts tree belowground C allocation to ectomycorrhizal fungi, and to long-term N-loading, which may have negative effects on both mycorrhizal and saprotrophic fungi. These results, therefore, question the use of ergosterol to monitor effects of soil perturbations on fungi in the field, but do not put into question the use of the biomarker in natural forest ecosystems.