Florida manatees, Trichechus manatus latirostris, respond to approaching vessels

Florida manatees inhabit shallow coastal and estuarine waters of the southeast US, a range that brings them into frequent contact with vessels. More than 30% of documented annual mortalities are attributed to vessel collisions, and most living animals bear the scars of multiple, non-lethal encounters. To document the behavior of manatees in the presence of vessels, we recorded their movements with an overhead video system. We scored six aspects of behavior during 170 vessel approaches, and compared their behavior with 187 control segments when no boats were present. Manatees in shallow waters and at the edge of the channel responded to approaches by orienting towards the nearest deep water, a boat channel, and increasing their swimming speed. Close boat approaches and shallow water depths exacerbated these responses. Our results indicate that manatees detect and respond to approaching vessels with an apparent flight response, a response which includes movement towards deeper water. If given sufficient time, i.e., approached or passed slowly, the manatees may then be able to reach deeper water and safe depths.     

The Efficacy of the Four-Part Test Network to Monitor Water Quality in the Loxahatchee National Wildlife Refuge

The Loxahatchee National Wildlife Refuge (Refuge) is impacted by inflows containing elevated contaminant concentrations originating from agricultural and urban areas. Water quality was analyzed using the Enhanced Refuge (ERN), the four-part test (FPTN), and the Consent Decree (CDN) monitoring networks within four zones in the Refuge. The zones were defined as the canal surrounding the marsh, the perimeter, the transition, and the interior zones. Although regression coefficients for ALK and SpC, and Ca, Cl, and SO₄ concentrations with distance from the canal were lower using the FPTN than when using the ERN, using the FPTN to measure water quality parameters in the Refuge would give similar results as the ERN. Most of the ERN and FPTN sites are located in the northern and central areas of the Refuge. Water is deeper in the southern Refuge, and on an area basis contains a greater volume of water than the northern and central Refuge and therefore, water flow from the canal into the marsh in the northern and southern Refuge may differ. Numerous water quality monitoring sites must be added to the ERN and FPTN in the southern area to characterize water quality in the southern Refuge with confidence.     

Water Quality Characterization in the Northern Florida Everglades

The Loxahatchee National Wildlife Refuge (Refuge) developed as a system with waters low in nutrients. Today, the Refuge wetlands are impacted by inflows containing elevated nutrient concentrations originating from agricultural sources flowing into canals surrounding the west side and from urban and horticultural areas flowing into canals surrounding the eastern side of the Refuge. We analyzed water quality sampled at 40 sites divided into eastern and western areas and four zones in the Refuge. We defined four zones as the canals surrounding the Refuge marsh, the perimeter zone, the transition zone, and the interior zone. The canal receiving agricultural inflows had greater alkalinity and conductivity (SpC), Si and SO₄ but lower turbidity and total suspended solids than the canal receiving urban and horticultural inflows. Alkalinity, total dissolved solids (TDS), SpC, Ca, Cl, and SO₄ concentrations were greater in the perimeter than in transition and interior zones. Alkalinity and SpC values and SO₄ concentrations were greater in the transition than in interior zone. Alkalinity, SpC, and TDS values and Ca, SO₄, and Cl concentrations correlated in negative curvilinear relationships with distance from the canal (r ²?=?0.78, 0.70, 0.61, 0.78, 0.64, 0.57, respectively). Analysis of multiple water quality parameters may reveal the complexity of interactions that might be overlooked in a simple single parameter analysis. These data show an impact of canal water containing high nutrient concentrations on water quality flowing from the canal towards the Refuge interior.     

Water Quality Gradients in the Northern Florida Everglades

The Loxahatchee National Wildlife Refuge (Refuge) developed as a system with waters low in nutrients. Today, the Refuge wetlands are impacted by inflows containing elevated nutrient concentrations originating from agricultural sources. We analyzed water quality sampled at 54 sites in the Refuge. The Refuge was divided into northern, central, and southern latitudinal areas and then perimeter, transition, and the interior zones based on distance from the canal towards the Refuge interior. In the perimeter zone, total dissolved solids (TDS), silicon (Si), and total phosphorus (TP) concentrations in water were higher in the northern than the central area and TDS, Si, SO₄, and TP concentrations in water were higher in the central than the southern area. In general TDS, Ca, Cl, Si, SO₄, and TP loads in the northern perimeter, transition, and interior zones decreased from 2005 to 2009. The decrease is less pronounced in the central and southern areas than the northern area. As water flowed southward for over 30?km from the northern to the southern area in the perimeter zone, most water quality parameters analyzed were reduced in the water column. However, large amounts of Ca and Cl were added to the water column indicating that canal water is continually diffusing and intruding into the Refuge in all zones. In the perimeter zone, and to a lesser degree in the transition zone, the Refuge has accumulated substantial amounts of Ca, Si, SO₄, and TP in vegetation and soils during the sampling period.     

Water Quality Trends in the Loxahatchee National Wildlife Refuge

The Loxahatchee National Wildlife Refuge (Refuge) developed throughout millennia as a system with waters low in nutrients. Today, the Refuge wetlands are impacted by inflows containing elevated nutrient concentrations originating from agricultural sources. Surface water samples were collected monthly at 48 marsh and five canal sites from June, 2004 through May, 2011 and analyzed water quality trends by sampling perimeter, transition, and the interior zones based on distance from the canal towards the Refuge interior. Nutrient, inorganic ion, and C concentrations generally decreased with distance from the canal to the Refuge interior. These water quality parameters also decreased from the canal to the Refuge interior, but less sharply. This finding suggests that there has been less canal water intrusion into the Refuge during the sampling period. The origin of the high Ca and Cl concentrations in canal water is most likely from intrusion of connate seawater into the canal. The reason for the improved water quality from June, 2004 to June 2011 can be attributed to an improved STA1-East performance since 2005. Additionally, canal water that originally by-passed treatment in STA1-East and STA1-West, and flowed into the L-7 canal through the S-6 pump, is now diverted farther south into STA2 for treatment.     

Estimating relative energetic costs of human disturbance to killer whales (Orcinus orca)

This study examined the activities of “northern resident” killer whales (Orcinus orca) in Johnstone Strait, British Columbia, Canada, in July and August, from 1995 to 2002. Disturbance from boat traffic has been identified as a conservation concern for this population. The primary aims of the study were to test whether boat presence altered whales’ activities, and if so, to estimate whether behavioural responses were likely to have carried energetic costs. A land-based observation site near a vessel-exclusion marine protected area allowed us to conduct a natural experiment to monitor whale activities in the presence and absence of boats. Using Time-Discrete Markov Chain models, boat presence was linked to significant changes in the probability that focal whales would switch from one activity state to another, which led to significantly different activity budgets in the presence and absence of boats. We estimated that the energetic cost of meeting these budgets differed by only 3-4%. In the presence of boats, however, whales reduced their time spent feeding and the time spent rubbing their bodies on smooth pebble beaches. These lost feeding opportunities could have resulted in a substantial (18%) estimated decrease in energy intake. Our sensitivity analysis provides preliminary evidence that disturbance could carry higher costs to killer whales in terms of reducing energy acquisition than increasing energetic demand, and future research should address this directly. Meanwhile, our observations suggest that protected areas would confer greatest conservation benefit to endangered killer whale populations if they were designed to protect important foraging areas.     

Factors associated with survival of reintroduced riparian brush rabbits in California

The riparian brush rabbit (Sylvilagus bachmani riparius) is an endangered species found in dense, brushy habitat in the California’s Central Valley. We implemented a reintroduction program to bolster populations at a Federal Wildlife Refuge and to assess factors influencing mortality and subsequent survival of released individuals. Between July 2002 and July 2005, we reintroduced 325 captive-bred individuals to unoccupied habitat within their historic range using a soft-release strategy and monitored their subsequent survival with radiotelemetry. Longer time in soft-release pens resulted in increased monthly survival. Rabbits were most susceptible to post-release mortality during the first 4 weeks following reintroduction and both body mass and length of time in the soft-release enclosure influenced this relationship. When we controlled for release mortality during this acclimation period, subsequent monthly survival probabilities were most strongly influenced by release year (year 1 vs. years 2 and 3) and by a catastrophic flooding event; length of time in the soft-release enclosure remained an important variable in longer-term survival. Cause of mortality was unknown for the majority of deaths (61.9%), but predation (including presumptive predation) was the greatest known cause of death in translocated rabbits (26.4%). Reintroduction programs should employ an adaptive management approach with ongoing monitoring of target animals and concurrent analysis to allow managers to adjust methods as conditions dictate.     

Development of predictive models to explain the distribution of the West Indian manatee Trichechus manatus in tropical watercourses

Logistic regressions were used to study the relationship between habitat variables and the use of tropical watercourses by the West Indian manatee Trichechus manatus at Northeastern Costa Rica and Southern Nicaragua. Presence of manatees in watercourses was assessed through direct and reported sightings of individuals and feeding signs on aquatic vegetation. Indirect methods provided good approximations to the actual distribution that could not have been achieved through direct observations or aerial surveys. Best multivariate models showed that manatees were most present in watercourses that presented abundant aquatic vegetation, warm, and clear waters, high forest cover, and are wider than those where the species is absent. Although habitat variables that explain habitat use of manatees differed for the two sectors found within the study area, manatees preferred lagoons to other watercourses in both areas. These findings point to forest clearing on the shores as a threat for manatee conservation. Habitat variables are excellent predictors of manatee presence, and predictive models as those developed in this study can help assess potential distribution of manatees in areas where this information is lacking as well as to assist identify potential reintroduction areas.     

Spatial patterns of ecohydrologic properties on a hillslope-alluvial fan transect,central New Mexico

Spatial patterns of soil properties are linked to patchy vegetation in arid and semi-arid landscapes. The patterns of soil properties are generally assumed to be linked to the ecohydrological functioning of patchy dryland vegetation ecosystems. We studied the effects of vegetation canopy, its spatial pattern, and landforms on soil properties affecting overland flow and infiltration in shrublands at the Sevilleta National Wildlife Refuge/LTER in central New Mexico, USA. We studied the patterns of microtopography and saturated conductivity (Ksat), and generally found it to be affected by vegetation canopy and pattern, as well as landform type. On gently sloping alluvial fans, both microtopography and Ksat are high under vegetation canopy and decay with distance from plant center. On steeper hillslope landforms, only microtopography was significantly higher under vegetation canopy, while there was no significant difference in Ksat between vegetation and interspaces. Using geostatistics, we found that the spatial pattern of soil properties was determined by the spatial pattern of vegetation. Most importantly, the effects of vegetation were present in the unvegetated interspaces 2–4 times the extent of vegetation canopy, on the order of 2–3 m. Our results have implications for the understanding the ecohydrologic function of semi-arid ecosystems as well as the parameterization of hydrologic models.     

Effects of planting method and seed mix richness on the early stages of tallgrass prairie restoration

Tallgrass prairie restoration has been practiced for more than 75 years, yet few studies have systematically tested restoration methods over large geographic regions with the intent of refining methodology. In this study, we used three planting methods (dormant-season broadcast, growing-season broadcast and growing-season drill) fully crossed with three levels of seed species richness (10, 20, and 34 spp). We replicated the study on nine former agricultural fields located from east-central Iowa (Neal Smith National Wildlife Refuge) to northwestern Minnesota (Litchfield, Fergus Falls and Morris Wetland Management Districts), USA, within the northern tallgrass prairie biome. Objectives were to evaluate the relative influences of planting method, seed mix richness, and their interactions, on (1) planted cover (both total and by guild) and richness, (2) exotic species cover, and (3) non-planted native species cover. Optimal techniques varied between the two study areas: the dormant broadcast method produced greater cover of planted species at the Minnesota sites and the growing-season drill method produced greater cover of planted species at Iowa sites. The dormant broadcast method strongly favored establishment of perennial forbs while the growing-season drill favored warm-season grasses. Although increasing richness of the seed mix produced greater planted species richness, this did not result in greater resistance to exotic invasion. We conclude that, if planting during the growing season, drilling seed is preferable to broadcasting, but if the choice is between broadcasting seed in the dormant or growing season, the dormant season is preferred.     

Dolphin-watching tour boats change bottlenose dolphin (Tursiops truncatus) behaviour

Over the last decade there has been considerable growth in marine mammal-watching tourism throughout the world. Due to the species use of coastal habitats, bottlenose dolphins are most frequently exposed to dolphin-watching tourism. We conducted boat-based focal follows of schools of bottlenose dolphins to determine the effect of boats on dolphin behaviour. A CATMOD analysis showed that behaviour differed by boat number, in particular, resting behaviour decreased as boat number increased. Dolphins rested less and engaged in more milling behaviour in the presence of permitted dolphin-watching boats compared to non-permitted boats. An increase from 49 to 70 permitted trips per week and a change in their departure times resulted in a further decrease in resting behaviour. Currently the effects of boats, in particular permitted boats, on dolphin resting behaviour whilst they are in the Bay of Islands, are substantial. In the light of these findings we suggest that current legislation in New Zealand is not affording this isolated population protection from disturbance.     

Status of the West Indian Manatee in Honduras

Aerial surveys and interviews with fisherman in Honduras indicate that manatee numbers are low. There is an abundance of suitable habitat, and evidence on the proportion of calves indicates that manatees are reproducing. Although natural mortality occurs when the animals are trapped in small landlocked coastal lagoons, the greatest threat to manatees is from subsistence hunting for their meat. Harpooning from a small motorised canoe is the most common means of capture; however, entanglement in gill nets may also be employed. Enforcement of existing protective laws and enlistment of public support is required to preserve the remaining manatees in Honduras.     

不同调理剂对猪粪好氧堆肥效果的影响

分别以木屑、药渣、菇渣、砻糠灰作为猪粪堆肥的调理剂,研究其在堆肥过程中温度、含水率、pH、EC和主要营养元素N、P、K的动态变化。结果表明,在整个堆制过程中,4个处理的堆温变化明显呈现出升温期、高温期和降温期3个阶段,其中,木屑处理堆体升温最快,且高温持续时间最长,砻糠灰处理高温持续时间最短;与初始值相比,堆肥后每个处理pH均有所上升,其中菇渣处理上升幅度最大,达0.9个单位;堆制过程中,4个处理有机质总体呈现下降的规律;堆肥后药渣处理的TN和TP含量最高;堆肥后砻糠灰处理的TK含量最高;堆肥后4个处理的pH和EC值都在腐熟堆肥的适宜范围之内,从N+P2O5+K2O总养分和保氮角度来看,应选药渣作调理剂,从提高堆肥TK含量来看,应选砻糠灰作调理剂。     

虾夷扇贝浮筏养殖作业改造与试验

该文针对目前虾夷扇贝(Patinopecten yessoensis)浮筏养殖作业用工量大、劳动强度高、工作效率低、耗能高以及尾气和噪音污染严重等问题,通过对獐子岛虾夷扇贝浮筏养殖作业工作模式与回收养殖吊笼方式的调研,提出了虾夷扇贝浮筏养殖作业的改进方案,并通过海上生产对比试验,得出以下结论:第1阶段以8 m长浮筏养殖作业船为母船,安装了电动拔梗装置、拔笼装置、抖笼装置、筛苗装置以及齿形滑轮滑梗装置,改变单纯依靠人力工作的作业模式为机械化作业模式,不仅用工人数及劳动强度大幅降低,并且拔笼量较原浮筏养殖作业平均每天单船提高了56.01%,耗能费用降低了13.95%;第2阶段在保留第1阶段机械化设备的基础上,对养殖作业船只的作业模式进行了改造,用船长12 m、船宽3.3 m、型深0.7 m,尾挂机型号洋马/CY1115,最大功率16.2 kW的作业船代替了原来船长8 m、船宽2.4 m、型深0.5 m,尾挂机型号ZS195,最大功率9.7kW的作业船,并省去了辅助运输船舶,将养殖作业和辅助运输合并为一条船。试验结果显示,拔笼数量较第1阶段改造的浮筏养殖作业模式平均每天单船提高了31.69%,较原浮筏养殖作业模式平均每天单船拔笼量提高了1.05倍。第2阶段改造的浮筏养殖作业船的装载和运输能力满足实际工作需求,平均每天单船耗能费用与第1阶段改造的浮筏养殖作业模式无显著性差异,较原浮筏养殖作业模式降低了14.12%。同时第2阶段改造的浮筏养殖作业模式较原浮筏养殖作业模式其单船年节省费用1.08万元。由此说明改造后的浮筏养殖作业装备及作业方式具有节能、高效等特点,推广应用前景广阔。     

Reefs of an uninhabited Caribbean island: fishes, benthic habitat, and opportunities to discern reef fishery impact

Navassa Island is a tiny, (5 km²) uninhabited US protectorate located between Jamaica and Haiti. It is part of the Caribbean Islands National Wildlife Refuge, under the jurisdiction of the US Fish and Wildlife Service. We conducted a quantitative assessment of Navassa's coral reef fishes and benthic habitat, in order to assist with the development of conservation plan for the island. The shallow reefs of Navassa (<23m) have high live coral cover (range 20-26.1%), high degree of architectural complexity (rugosity index range 1.4-1.9), and moderate abundance of the keystone grazing urchin, Diadema antillarum, at all sites (mean 2.9±0.9 per 30 m²). Despite its remoteness, an unregulated, artisanal fishery (primarily using traps and hook and line) carried out by Haitians is the primary mode of human impact on Navassa reefs. Even so, reef fish communities exhibit high density (range 97-140 fish per 60 m²) and retain representation by large snapper, grouper and herbivores, which are mostly lacking in nearby Caribbean locations with high fishing pressure. Thus, Navassa reefs appear to be trophically intact with fish populations relatively “unexploited,” presenting a conservation challenge and a research opportunity. The regulation and conservation of the fishery will be difficult, due to the international nature of the situation. However, given the apparently small impact that artisanal fisheries have yet had on its reef communities, Navassa presents a possibly unique opportunity to study the ecological functioning of a relatively trophically intact Caribbean reef, and represents a strong imperative for conservation, monitoring, and research.     

Lizard assemblage and reserve size and structure in the Western Australian wheatbelt — some implications for conservation

Twenty-three reserves in the Western Australian wheatbelt were examined in detail to evaluate the adequacy of the reserve system in the region for the conservation of lizards. We recorded most of the lizard species known from the region and conclude that the reserve system is at present adequate for their conservation.Lizard species richness in wheatbelt reserves does not appear to be related to isolation from adjacent uncleared land, either in space or time, but is related to the ecology of the reserve. Lizard species richness-area relationships for wheatbelt reserves are very similar to the most comparable late-Pleistocene/Holocene continental island lizard faunas; the slopes of the regression lines are not significantly different and the intercepts are only marginally significant.Multiple regression analysis shows that 75% of the variation observed in lizard species richness between reserves is accounted for by the algorithm of the number of vegetation associations on these reserves; addition of other reserve variables examined (including area) does not significantly increase this explained variation.Reserves as small as 30 ha are valuable as sanctuaries for lizards although it is suggested that 1500 ha is an optimum size. Some vegetation formations are more important for lizards than others; woodlands are most important.     

The role of social aggregations and protected areas in killer whale conservation: The mixed blessing of critical habitat

Protected areas are often proposed as tools for conserving endangered populations of marine megafauna. Our study area includes a voluntary no-entry reserve embedded within wider critical habitat for Threatened ‘northern resident’ killer whales under Canada’s Species at Risk Act. Our study quantified the reserve’s importance to whales by assessing habitat preference in a behavioural context, and population-level implications of that preference given threats from human activities, such as oil spills resulting from shipping traffic. We recorded summertime activities of whales from 1995 to 2002. Whales were observed on 397 of 530 (74.9%) days. Whales showed strong preference for the reserve over adjacent waters, and used it preferentially for feeding and beach-rubbing. While the area comprises ∼0.001% of the whales’ range, an overall average of 6.5% of the population was present each day. Frequently, >50% of this small population was aggregated in the restricted and heavily trafficked waterway of Johnstone Strait. Using the Potential Biological Removal equation, we calculated potential annual mortality limits (ML) of 2.2 animals. Mean group size in the area exceeded ML on 55.8% of days overall, and 98.8% of days when conditioning on whale presence. The whales’ high reliance on a trivial fraction of their range means that opportunities are routine for one stochastic, catastrophic event to cause population decline. On 20 August 2007, a barge loaded with ∼10,000 L of diesel sank in the area, exposing 25% of the population. This underscores the importance of identifying critical habitat for threatened populations, and ensuring meaningful protection.     

Monitoring predators to optimize their management for marine turtle nest protection

The fundamental conservation focus for Hobe Sound National Wildlife Refuge (HSNWR), Florida is to provide protected nesting habitat for three threatened or endangered marine turtle species. Turtle nesting and hatching spans from early spring to fall each year. Left unchecked, nest predation by raccoons and armadillos would destroy most turtle nests. Predators are removed to protect nests, primarily with a one person-month contract using control specialists. We maximized the efficiency of predator removal by using a passive tracking index to: (1) optimize the timing and strategy for predator removal, (2) minimize labor by identifying areas where predator removal would have maximal effect, (3) examine beach invasion patterns of predators, (4) assess efficacy of removal efforts, (5) provide anticipatory information for future turtle nesting seasons, and (6) serve as a detection method for invasion by additional species known to depredate turtle nests. An overall nest predation rate of 28% resulted, whereas the rate for the previous year was 42% when the same level of contracted predator removal was applied, but without monitoring predators. One year before that, predator removal was done without contracts with specialists and predation was 48%. Up to 95% of the nests were destroyed in the years prior to predator removal. Using 2000 data on numbers of nests, clutch sizes, and emergence rates, we estimated the number of hatchlings that would have been lost assuming that the predation rates observed from four predator removal scenarios at HSNWR would have occurred in 2000. Historical predation of 95% would have resulted in 120,597 hatchlings lost in 2000. Predator removal as part of regular refuge operations would have reduced this number to 62,481. Addition of a contract with control specialists would have further reduced the number lost to 53,778. Addition of temporal and spatial monitoring for predator removal reduced losses to 36,637.     

Disturbance to a foraging seabird by sea-based tourism: Implications for reserve management in marine protected areas

The provision of recreational opportunities is one of the important human goals of marine protected areas. However, as levels of recreational use increase, human disturbance is likely to cause significant detrimental effects upon wildlife. Here we evaluate the best managing options to mitigate the impact of sea-based tourism on the foraging activity of an endangered population of European shags, Phalacrocorax aristotelis, in a coastal marine protected area (Cíes islands, north-western Iberia). Boat disturbance elicited a characteristic avoidance behavior that resulted in a substantial reduction in foraging activity as levels of boat use increased. Moreover, boats excluded shags from the best feeding areas, resulting in higher densities of foragers in areas of little boat traffic. We used a behavioral model to explore the effects of managing strategies aimed at reducing the impact of boats on the foraging activity of shags. Our model suggested that in low boat disturbance scenarios limiting the number of boats using the reserve would be a better management option than habitat protection (i.e. the establishment of set-aside areas free of boat traffic). On the contrary, when boat disturbance levels are high the protection of habitat is recommendable, even if spatial variation in habitat quality is unknown or poorly assessed. Our study stresses the point that management strategies to minimize disturbance to foraging seabirds may depend on the spatial overlap between sea-based recreational activities and foraging seabirds and the spatial variation in marine habitat quality for seabirds.     

Tolerance of West Indian manatees to capture and handling

Ninety-two West Indian manatees (Trichechus manatus) have been captured in the southeastern United States from October 1975 through November 1983 with no evidence of an unusual susceptibility to capture myopathy. Of these, 53 were radio-tracked or observed in the field following capture with no evidence of delayed capture stress. Blood samples obtained at capture for 20 wild individuals displayed no elevation in biochemical variables typically seen in mammalian capture myopathy cases. Thirty-one manatees captured for rescue and rehabilitation generally did not exhibit symptoms of capture myopathy, although in one case marked elevations in creatinine phosphokinase were observed, probably related to lengthy transport. Necropsy findings for 20 terminal cases that died of various causes unrelated to their rescue or handling did not indicate the involvement of any gross or histological lesions of capture myopathy. Historical records for the capture and handling of about 150 West Indian manatees during the 1900s also suggest a tolerance to these activities. Recent observations on the probable susceptibility of dugongs (Dugong dugon) to capture stress apparently cannot be extended to West Indian manatees.