Reducing longline bycatch: The larger the hook, the fewer the stingrays

Chondrichthyan populations in the Mediterranean Sea have been heavily affected by the impact of fishing activities. In the last two decades, even fishing gears that were traditionally considered highly selective, such as pelagic longlines, have been revealed to be responsible for the capture of many unwanted species. The pelagic stingray (Pteroplatytrygon violacea) is not an endangered nor a charismatic species, but it largely dominates longlines bycatch fractions.The aim of our study was to investigate the importance of three main variables, bait size, presence and type of light attractors, and hook size and shape, in the capture rate of pelagic stingrays. Ninety-seven longline experimental sets were run. Trials took place on nine vessels in the Strait of Sicily, central Mediterranean Sea, over a period of 3 years from 2005 to 2007. Results showed that the larger the J hook, the lower the stingray capture rate. Moreover, 16/0 circle hooks had a significantly lower number of stingrays captured per 1000 hooks than J hooks, up to ∼80%. Bait size, within the range of sizes assessed, and use of light attractors did not have significant effects on stingray catch rate. These results suggest that the adoption of large circle hooks by commercial and artisanal swordfish longlining may be a measure to reduce their environmental footprint.     

An alternative to dolphin oil as a fish attractant in the Ganges River system: conservation of the Ganges River dolphin

Oil extracted from blubber of the Ganges River dolphin, Platanista gangetica, is used as a fish attractant in India and Bangladesh. This oil fishery is associated with the mortality of hundreds of dolphins every year. Oil from fish scraps was field tested for 121 days during 1997-1999 in the Ganges at Patna and was a very effective alternative to dolphin oil as a fish attractant. Fishing with fish oil resulted in higher catches and greater income per person per hour (Rs. 17.8±12.5) than fishing with dolphin oil (Rs. 11.6±9.3). However, there is no statistically significant difference between the results from fishing with dolphin and fish oil. Oil from fish scraps is inexpensive and can be made readily available to all the fishermen. Its widespread use would help in conserving the endangered Ganges River dolphin.     

Genetic variation in the endangered Inner Mongolia endemic shrub Tetraena mongolica Maxim. (Zygophyllaceae)

Tetraena mongolica Maxim, is a critically endangered and endemic species of westem Inner Mongolia in China. Genetic variability within and among eight extant populations of this species was assessed using ISSR PCR (13 primers). We expected a low genetic diversity level, but our results revealed an intermediate level of intraspecific genetic diversity, probably resulting from this species being in a refuge during the last glaciation (at population level: P=48.1%, A_e=1.305, H_E=0.177 and H_pop=0.264; at species level: P=63.3%, A=1.368, H_T=0.213 and Hsp=0.324). A low level of genetic differentiation among populations was detected based on Nei's genetic diversity analysis (16.91%), Shannon's diversity index (18.83%) and AMOVA (15.2%). Populations shared high levels of genetic identity (I=0.9516±0.013). The extensive gene flow was a plausible reason for the low genetic differentiation.     

Effects of Key deer herbivory on forest communities in the lower Florida Keys

Ungulate herbivory can have strong impacts on plant communities, but these impacts are rarely considered in recovery plans of endangered species. This study examined the effects of the endangered Key deer (Odocoileus virginianus clavium) on its environment in the lower Florida Keys. The Key deer population has increased to over 700 deer from approximately 50 deer in the 1950s; however, approximately 75% of the population resides on only a few islands (Big Pine, No Name, Big Munson) where Key deer herbivory on forest communities may be substantial. Effects of deer herbivory on plant densities were estimated on these islands using vegetation quadrats in hardwood hammock, buttonwood transition, and mangrove wetlands and compared to nine other islands with intermediate or low deer densities. On islands with high deer density, densities of preferred woody plant species <1.2 m tall (within Key deer reach) were significantly lower than islands with lower deer densities, while densities of some nonpreferred species were significantly higher. Deer exclosures established in hardwood hammock on a high-density deer island revealed a mean increase in abundance/height of preferred woody species inside exclosures, while nonpreferred species significantly increased in open plots. We conclude that on high deer density islands, highly preferred plant species might eventually fail to regenerate and unpalatable plant species may become dominant. Careful criteria need to be developed to maintain Key deer numbers above an endangered species status yet below levels that are destructive to local forest species.     

Herbicides, weeds and endangered species: management of bitou bush (Chrysanthemoides monilifera ssp. rotundata) with glyphosate and impacts on the endangered shrub, Pimelea spicata

Environmental weed invasion threatens the biodiversity of native species. Unfortunately, managing these weeds may also affect biodiversity adversely. A recent example occurred when glyphosate, a herbicide used to control the highly invasive weed, bitou bush (Chrysanthemoides monilifera ssp. rotundata), accidentally drifted over a small population of an endangered shrub, Pimelea spicata. Following concerns that the affected population would not recover and, thereby, cause the local extinction of P. spicata, we conducted a series of glasshouse and field experiments to explore the impacts of glyphosate on this endangered species. Seedlings and young plants of P. spicata, in which the tap root was undeveloped, were killed by a single application of glyphosate. Older plants with a well developed tap root also died back initially, but about 50% of individuals re-sprouted. This re-growth was associated with a significant decrease in tap root diameter, implying that further disturbance, including repeated treatment with glyphosate, would kill plants by impairing their potential for recovery. Unlike some sclerophyllous native shrubs, the tolerance of P. spicata to glyphosate was limited, even when its growth was slowed artificially by limiting water availability. Winter applications of glyphosate to manage infestations of bitou bush will impact adversely on populations of P. spicata and may also affect the other rare and endangered species whose survival is threatened by this species, even though some natives are unaffected by the herbicide. Protecting native biodiversity from bitou bush will involve sustainable weed management that minimises impacts on non-target native species.     

Effects of an exotic prey species on a native specialist: Example of the snail kite

Despite acknowledging that exotic species can exhibit tremendous influence over native populations, few case studies have clearly demonstrated the effects of exotic prey species on native predators. We examined the effects of the recently introduced island apple snail (Pomacea insularum) on the foraging behavior and energetics of the endangered snail kite (Rostrhamus sociabilis plumbeus) in Florida. We conducted time-activity budgets: (i) on kites foraging for native Florida apple snails (Pomacea paludosa) in major wetland units within the kites’ range that had not been invaded by the exotic island apple snail and (ii) on kites foraging for exotic apple snails in Lake Tohopekaliga, the only major wetland utilized by the snail kite that had suffered a serious invasion of P. insularum. When foraging for P. insularum, snail kites dropped a greater proportion of snails, and they experienced increased handling times and decreased consumption rates; however, kites foraging for P. insularum also spent a smaller proportion of the day in flight. Estimates of net daily energy balances between kites feeding on P. insularum versus P. paludosa were comparable for adults, but juveniles experienced energetic deficiencies when feeding on the exotic snail. Due to this discrepancy, we hypothesize that wetlands invaded by P. insularum, such as Lake Tohopekaliga, may function as ecological traps for the snail kite in Florida by attracting breeding adults but simultaneously depressing juvenile survival. This study highlights the conservation implications and importance of elucidating the effects that exotic species have on native specialists, especially those that are endangered, because subtle influences on behavior may have significant population consequences.     

Location of roosts of the lesser long-eared bat Nyctophilus geoffroyi and Gould's wattled bat Chalinolobus gouldii in a fragmented landscape in south-eastern Australia

The location of roosts of two species of vespertilionid bats, the lesser long-eared bat (Nyctophilus geoffroyi) and Gould’s wattled bat (Chalinolobus gouldii), was investigated in a remnant vegetation-farmland mosaic and adjacent floodplain forest in south-eastern Australia. A total of 45 individuals of N. geoffroyi and 27 C. gouldii were fitted with radio transmitters, which resulted in the location of 139 and 89 roosts respectively. Selection of roosting habitat showed both inter- and intra-specific differences. At the landscape level, locations of roosts used by male and female N. geoffroyi differed markedly. Most males roosted in the farmland mosaic within 3 km (mean 1.9±2.9 km) of where they were captured while foraging in remnant vegetation. In contrast, roost sites of females were predominantly in the floodplain forest, 6-12 km from their capture site in farmland (mean for all females, 6.7±2.9 km). All maternity roosts were in the extensive floodplain forest, 4-10 km from foraging areas. Distances moved by this species were greater than previously recorded and further than predicted by flight morphology. Most C. gouldii roosted in the floodplain forest, 4-10 km from their capture site (6.9±1.6 km). Within the floodplain forest, both species roosted in areas that had higher densities of hollow-bearing trees than generally available; dead hollow-bearing trees for N. geoffroyi and large, live trees for C. gouldii. The scale of movements undertaken by these species means that they can obtain resources from multiple landscape elements. Both species used different habitats for roosting and foraging despite the energetic costs of commuting relatively large distances. Conservation of bat populations in rural environments needs to be considered at the landscape scale, with particular attention to identifying landscape elements that provide key resources.     

Driftnet fishing and biodiversity conservation: the case study of the large-scale Moroccan driftnet fleet operating in the Alboran Sea (SW Mediterranean)

Illegal, large-scale driftnets are still used in several Mediterranean areas. According to international official sources, Morocco harbors the bulk of this fleet in the Mediterranean. To ascertain its biodiversity impact, 369 fishing operations (worth 4140 km of driftnets set) made by the driftnet fleet targeting swordfish (Xiphias gladius) based in Al Hoceima (Alboran Sea) were monitored between December 2002 and September 2003. Parallel surveys were made in the main Mediterranean ports and in that of Tangiers, in the Gibraltar Straits, to estimate the total fishing effort. Results showed an active driftnet fleet conservatively estimated at 177 units. Estimated average net length ranges from 6.5 to 7.1 km, depending on the port, though actual figures are suspected to be much higher (12-14 km). Most boats perform driftnet fishing all year round, resulting in very high annual effort levels. A total of 237 dolphins (short-beaked common dolphin, Delphinus delphis, and striped dolphin, Stenella coeruleoalba), 498 blue sharks (Prionace glauca), 542 shortfin makos (Isurus oxyrinchus) and 464 thresher sharks (Alopias vulpinus) were killed by the boats monitored during the sampling period, during the peak of the swordfish fishery, along with 2990 swordfish. Loggerhead turtle (Caretta caretta) was also caught (46 individuals). Estimates for a 12-month period by the whole driftnet fleet yielded 3110-4184 dolphins (both species) and 20,262-25,610 pelagic sharks distributed in roughly equal proportions for P. glauca, I. oxyrinchus and A. vulpinus, in the Alboran Sea alone; further 11,589-15,127 dolphins and 62,393-92,601 sharks would be killed annually around the Straits of Gibraltar. Dolphins suffer from annual take rates exceeding 10% of their population sizes in the Alboran Sea; this unsustainable impact is particularly worrying for D. delphis, because its last remnant healthy population in the Mediterranean occurs in this area. Average catch rate for swordfish, the main target species, amounted to only 0.8 individuals/km net set. Pelagic sharks are actively targeted by a part of the fleet.     

Experimental management of Mediterranean temporary pools for conservation of the rare quillwort Isoetes setacea

Mediterranean temporary pools represent unique species-rich habitats with many rare and endangered species. The Roque-Haute Natural Reserve is one of the few sites in France with Isoetes setacea Lam., a very rare Mediterranean quillwort, considered as a keystone species determining a priority habitat for the European Union. Land uses changes have favoured the invasion of the pools by several shrub and tree species (e.g., Ulmus minor, Fraxinus angustifolia subsp. oxycarpa). Clearing shrubs in an experimental area of one pool resulted in the increase of I. setacea as compared to control, combining a higher cover in previously occupied quadrats and more quadrats occupied. Litter accumulation had a negative effect on the population of Isoetes but this effect was detectable only in the cleared area. Light attenuation was shown experimentally to be detrimental to the vegetative and regenerative production of I. setacea. Clearing of the shrubs and removal of the litter led to an increase in the I. setacea populations and therefore appears to be an effective technique for restoring these plant communities invaded by shrubs. Long-term shrub control should be ensured by reintroducing sheep grazing in order to enhance the sustainable conservation of this oligotrophic habitat.     

Hybridization and conservation of Mediterranean orchids: Should we protect the orchid hybrids or the orchid hybrid zones?

Natural hybridization between plant species often occurs in disturbed habitats and it is generally considered a threat for rare and endangered species. A different situation occurs in Mediterranean food deceptive orchids, where hybridization is a common phenomenon, as a natural consequence of their unspecific pollination system.Here, we present molecular and ecological evidence from a hybrid zone between Orchis mascula and O. pauciflora in order to address the consequences of hybridization on local orchid evolution and to assess conservation priorities for hybrids and hybrid zones in orchid conservation programs.We find that, although hybrids among the two target taxa are formed relatively frequently, hybrid zones often consist of F1 individuals, whereas backcrosses and later generation hybrids appear to be either rare or absent, presumably as a consequence of post-zygotic reproductive barriers acting in these food-deceptive orchids. Experimental evidence further indicates that hybrids are less fit than the parental species in attracting pollinators and that parental taxa exhibit higher or similar fitness in sympatry compared to allopatric populations. Since introgression is not frequent as indicated by molecular analyses, fitness and phenotypic trait differences observed among sympatric and allopatric populations of the parental taxa may be a consequence of pollinator-mediated selection.Our experimental data confirm that hybridization is a natural phenomenon in food-deceptive orchids and that it does not pose a threat to their survival. Furthermore, sympatric zones provide the stage for evolutionary processes in orchids, and this peculiarity should be taken into account when devising orchid conservation strategies.     

What genetics tell us about the conservation of the critically endangered Balearic Shearwater?

The Balearic shearwater Puffinus mauretanicus is one of the most critically endangered seabirds in the world. The species is endemic to the Balearic archipelago, and conservation concerns are the low number of breeding pairs, the low adult survival, and the possible hybridization with a sibling species, the morphologically smaller Yelkouan shearwater (P. yelkouan). We sampled almost the entire breeding range of the species and analyzed the genetic variation at two mitochondrial DNA regions. No genetic evidence of population decline was found. Despite the observed philopatry, we detected a weak population structure mainly due to connectivity among colonies higher than expected, but also to a Pleistocene demographic expansion. Some colonies showed a high imbalance between immigration and emigration rates, suggesting spatial heterogeneity in patch quality. Genetic evidence of maternal introgression from the sibling species was reinforced, but almost only in a peripheral colony and not followed, at least to date, by the spread of the introgressed mtDNA lineages. Morphometric differences were not correlated with mtDNA haplotypes and introgression is probably due to a secondary contact between the two species several generations ago. Overall, results suggested that the very recent demographic decline in this critically endangered species has not yet decreased its genetic variability, and connectivity found among most colonies should help to reduce species extinction risk. Spreading of introgression should be monitored, but the species is not jeopardized at the moment by genetic factors and the major conservation actions should concentrate at enhancing adult survival.     

The impact of predation by introduced stoats on Hutton's shearwaters, New Zealand

The Hutton's shearwater Puffinus huttoni is an endangered species of burrowing petrel, that is threatened at its two remaining breeding colonies by the activity of introduced stoats Mustela erminea. Predation of eggs, chicks and adult shearwaters was studied over 10 consecutive breeding seasons (1989/1990-1998/1999) and resident stoats were radio-tracked in two seasons. Stoats were estimated to be killing on average 0.25% of breeding adults and 12% of chicks in each season. Population modeling of Hutton's shearwaters indicated that the estimated impact of this predation was a reduction in the potential yearly population growth rate of 0.86±0.22%. The overall average growth rate derived from the population model of 0.44%, suggests that the population is not in immediate risk of decline and controlling stoats within the colony need not be a priority for management.     

Reproductive biology and conservation implications of three endangered snapdragon species (Antirrhinum, Plantaginaceae)

About 32% of Antirrhinum species are considered to be endangered; however, no field studies have focused on their reproductive biology. In this work, several aspects of the reproductive biology (flowering phenology, floral biology, breeding system) and potential limits on seed quantity and quality (pollen limitation, inbreeding depression) were studied in natural populations of three endangered species of the genus (Antirrhinum charidemi, Antirrhinum subbaeticum, Antirrhinum valentinum). Results disclose that all three species need insect visitors for seed production since fruit set after autonomous self-pollination was lower than under hand cross-pollination. A. charidemi and A. valentinum were mainly self-incompatible, whereas A. subbaeticum was self-compatible but herkogamous. Supplementary pollination in open-pollinated flowers only increased fruit set and seed set relative to controls in a given population of A. valentinum. Preliminary data on inbreeding depression at early life-cycle stages of the self-compatible A. subbaeticum revealed that the cumulative level was low. Despite the three species being closely related and sharing many ecological characteristics, they show different mating systems, and different factors limit seed quantity and quality. Thus, caution should be taken when making a common conservation plan for a group of closely related taxa.     

Phylogenetic diversity of endangered and critically endangered southeast Asian softshell turtles (Trionychidae: Chitra)

The intense exploitation of turtles in Asian markets has contributed to declines in turtle populations across the continent. Three-quarters of Asia’s turtles are threatened and half are endangered. A recent workshop on the Asian turtle crisis identified taxonomic studies of widespread species as a priority for research because these low risk species may include unrecognized, narrowly distributed taxa of much higher concern. Chitra indica is a widely exploited softshell turtle (family Trionychidae) found across southern Asia. Individuals from Thailand have been described as a separate species, Chitra chitra, but this has not been universally accepted, and many sources consider Chitra monotypic. Phylogenetic analysis of sequence data from the mitochondrial ND4 gene revealed three deeply divergent, monophyletic lineages within Chitra: C. indica, C. chitra, and a third unnamed form from Myanmar. This new form is probably Critically Endangered, which highlights the importance of systematic studies in determining conservation priorities.     

Foraging ecology, economics and conservation of Indian wolves in the Bhal region of Gujarat, Western India

We determined the food habits of the endangered Indian wolf Canis lupus pallipes in the Bhal region of Gujarat, western India by analyzing 1246 wolf scats from five packs by estimating prey availability and by monitoring radio-tagged wolves from three packs for 1994 hour. The frequency of occurrence of blackbuck Antelope cervicapra remains in scats was 55.5%, followed by cattle (25.7%), nilgai Boselaphus tragocamelus (6.3%); and as others (<5%). The frequency of food items in scats of different wolf packs reflected their relative availability. For cattle the distinction between scavenging and predation was only possible through continuous monitoring. The average feeding interval obtained from monitoring was 3.6± 0.7 (S.E.) days and the average consumption/wolf/day was 1.8± 0.3 (S.E.) Kg. Adult male blackbuck formed most (70%) of the biomass consumed by wolves whereas cattle carcasses and cattle actually killed by wolves contributed 14 and 8%, respectively. Predation on cattle therefore was low and translated in an estimated loss of Rs. 821 (US$ 17) per village per annum. We propose that landscapes such as the Bhal with high wolf densities, high natural prey availability and consequently low human-wolf conflict levels should be prioritized as prime sites for wolf conservation efforts.     

Entanglement of monofilament fishing lines and coral death

This study examined the extent of damage by monofilament fishing lines on the cauliflower coral (Pocillopora meandrina) colonies at a popular cast fishing site in Oahu, Hawaii in March 1998. Sixty-five percent of coral colonies had fishing lines on their surface, and 80% of colonies were either entirely or partially dead. The percentage of entirely and partially dead colonies was positively correlated with the percentage of colonies entangled with fishing lines. Percent dead coral surface area was larger for colonies with fishing lines than colonies without fishing lines. In colonies with fishing lines, percent dead coral surface area was positively correlated with percent area with fishing lines. The high incidence of coral colonies with fishing lines and the three sets of significant results indicated destructive effects of monofilament fishing lines to P. meandrina corals. There is thus a clear case that reefs should be protected not only from the effects of excessive removal of fishes, but also from the effects of unsuccessful fishing that results in fishing-line entanglement on corals.     

Quantifying imperfect detection in an invasive pest fish and the implications for conservation management

In managing non-native species, surveillance programmes aim to minimise the opportunity for invasions to develop from initial introductions through early detection. However, this is dependent on surveillance methods being able to detect species at low levels of abundance to avoid false-negative recordings through imperfect detection. We investigated through field experimentation the ability to detect Pseudorasbora parva, a highly invasive pest fish in Europe, in relation to their known density and sampling method. Secure pond mesocosms of area 100 m² contained P. parva densities from 0.02 to 5.0 m⁻²; each density was in triplicate. These were searched using point sampling electric fishing and deployment of fish traps (non-baited and baited). No fish were captured at densities <0.5 m⁻² using any method and this was considered their detection threshold. Point sample electric fishing was the least effective detection method, producing high proportions of false-negative data even at high fish densities. Baited traps were the most effective detection method. Probability of detection of P. parva was 1.0 for baited traps at all densities >0.5 m⁻², whereas for electric fishing it only exceeded 0.95 at 5.0 m⁻² using high searching effort. These data reveal that small pest fishes such as P. parva may be prone to imperfect detection when at low densities and this is consistent with a number of other invasive species. This indicates the importance of designing surveillance programmes using methods of known statistical power to optimise conservation resource expenditure and enhance management outcomes.     

Do partial marine reserves protect reef fish assemblages?

Fish assemblages in the Mimiwhangata Marine Park, an area closed to commercial fishing but open to most forms of recreational fishing, were compared with adjacent fished areas. Two survey methodologies were used; baited underwater video and underwater visual census. Snapper (Pagrus auratus), the most heavily targeted fish species in the region, showed no difference in abundance or size between the Marine Park and adjacent control areas. When compared to the fully no-take Poor Knights Island Marine Reserve and two other reference areas open to all kinds of fishing (Cape Brett and the Mokohinau Islands), the abundance and size of snapper at the Marine Park were most similar to fished reference areas. In fact, the Marine Park had the lowest mean numbers and sizes of snapper of all areas, no-take or open to fishing. Baited underwater video found that pigfish (Bodianus unimaculatus), leatherjackets (Parika scaber) and trevally (Pseudocaranx dentex) were significantly more common in the Marine Park, than in the adjacent control areas. However, none of these species are heavily targeted by fishers. Underwater visual census found similar results with five species significantly more abundant in the Marine Park and five species more abundant outside the Marine Park. The lack of any recovery by snapper within the Marine Park, despite the exclusion of commercial fishers and restrictions on recreational fishing, indicates that partial closures are ineffective as conservation tools. The data suggest fishing pressure within the Marine Park is at least as high as at other ‘fished’ sites.     

Maximum foraging ranges in solitary bees: only few individuals have the capability to cover long foraging distances

To preserve populations of endangered bee species, sound knowledge of their maximum foraging distance between nest and host plants is crucial. Previous investigations predicted maximum foraging distances of 100-200 m for small bee species and up to 1100 m for very large species based on mainly indirect methods. The present study applied a new and direct approach to experimentally investigate maximum foraging distances in solitary bees. One endangered and two common species of different body sizes, all of which restrict pollen foraging to a single plant genus, were established in a landscape lacking their specific host plants. Females were forced to collect pollen on potted host plants that were successively placed in increasing distance from fixed nesting stands. The maximum foraging distance recorded for the small Hylaeus punctulatissimus was 1100 m, for the medium sized Chelostoma rapunculi 1275 m and for the large Hoplitis adunca 1400 m, indicating that maximum foraging distances at species level have been underestimated. However, the capability to use resources on such a large spatial scale applied only to a small percentage of individuals as 50% of the females of H. punctulatissimus and H. adunca did not forage at distances longer than 100-225 m and 300 m, respectively. This finding suggests that a close neighbourhood of nesting and foraging habitat within few hundred meters is crucial to maintain populations of these species, and that threshold distances at which half of the population discontinues foraging are a more meaningful parameter for conservation practice than the species specific maximum foraging distances.     

The regeneration status of the endangered Acer opalus subsp. granatense throughout its geographical distribution in the Iberian Peninsula

Acer opalus subsp. granatense is an endemic endangered tree with a wide but fragmented distribution in the Mediterranean mountains. The persistence of its small populations often depends on just a few adults, and consequently is highly vulnerable to factors limiting recruitment. In this paper, we examined the regeneration status of this maple in 16 populations throughout its whole geographical distribution in the Iberian Peninsula. Age and size structures were analysed as indicators of the viability of the species. Additionally, we studied the effects of herbivory by ungulates and the role of shrubs as nurse plants in maple regeneration dynamic. Our results show that A. opalus subsp. granatense has active recruitment throughout its range in the Iberian Peninsula. Shrubs served as the main microsites for recruitment, not only for early establishment but also for long-term survival. However, ungulates heavily damaged maple saplings in all locations and microhabitats. A direct consequence of herbivory is the uncoupling of age and size structures, saplings becoming older but not higher, possibly affecting population turnover in the long term. We suggest that the conservation of the small populations of Acer opalus subsp. granatense heavily depends on the control of herbivory pressure throughout the maple distribution area.