Establishing the ecological role of predators within an ecosystem is central to understanding community dynamics and is useful in designing effective management and conservation strategies. We ...analysed differences in the trophic ecology of four species of reef sharks (
Carcharhinus melanopterus
,
Carcharhinus amblyrhynchos
,
Triaenodon obesus
and
Negaprion acutidens
) at Ningaloo Reef, Western Australia, by analysing tissue stable isotopes (δ
15
N and δ
13
C). We also monitored animals using acoustic telemetry to determine long-term residency patterns in a bay at the southern end of the reef, Coral Bay. Overall, mean δ
13
C was similar among species, ranging between −10.9 and −11.8‰, suggesting a food-web dependency on coastal producers. Classification and regression tree analysis identified an effect of species on δ
15
N that separated
C. amblyrhynchos
and
C. melanopterus
from
N. acutidens
and
T. obesus
. For
C. amblyrhynchos
and
C. melanopterus
, animals were also divided by size classes, with smaller sharks having lower average δ
15
N than larger animals; this suggests that δ
15
N increases with size for these two species. Juvenile
C. melanopterus
, juvenile
N. acutidens
and adult
T. obesus
had trophic levels of 3.7, for juvenile
C. amblyrhynchos
and adult
C. melanopterus
it was 4, and adult
C. amblyrhynchos
had a value of 4.3. Trophic-level estimates for
C. melanopterus
and
C. amblyrhynchos
corroborate previous conclusions based on diet studies. We found no evidence for a difference in isotopic composition between resident and non-resident sharks. The lack of variation in isotopic composition was consistent with high mean residency of these species recorded using acoustic telemetry, which was 79% (±0.09 SE) of days monitored for
T. obesus
, followed by
N. acutidens
(57 ± 19.55%),
C. amblyrhynchos
(54 ± 13%) and
C. melanopterus
(33 ± 8.28%). High δ
13
C composition in reef sharks and long-term residency behaviour suggest that coastal marine reserves might provide effective conservation refuges for some species.
Grey reef sharks (Carcharhinus amblyrhynchos) are apex predators found on many Indo-Pacific coral reefs, but little is known about their movement patterns and habitat requirements. We used acoustic ...telemetry to determine movements and habitat use of these sharks at the isolated Rowley Shoals atolls, 250 km off the coast of north-western Australia. We equipped 12 male and 14 female sharks ranging from 0.79 to 1.69 m in total length with transmitters that were detected by an array of 11 strategically placed receivers on two atoll reefs. Over 26,000 detections were recorded over the 325 days of receiver deployment. No sharks were observed to move between reefs. Receivers on the outer slopes of reefs provided nearly all (99%) of the detections. We found no differences in general attendance parameters due to size, sex or reef, except for maximum period of detection where larger sharks were detected over a longer period than smaller sharks. Male and female sharks were often detected at separate receivers at the outer slope habitat of one reef, suggesting sexual segregation, but this pattern did not occur at the second reef where males and females were detected at similar frequencies. We identified two patterns of daily behaviour: (1) sharks were present at the reef both day and night or (2) sharks spent more time in attendance during day than at night. Fast Fourier transforms identified 24-h cycles of attendance at the reef and a secondary peak of attendance at 12 h for most sharks, although no individuals shared the same attendance patterns. Our study provides baseline data that can be used to optimise the minimum area and habitat requirements for conservation of these apex predators.
This study used a network of acoustic receivers deployed around a no‐take zone in Mangrove Bay, within the Ningaloo Reef Marine Park in Western Australia, to study residency and habitat preference of ...a small coastal shark, the nervous shark Carcharhinus cautus. Twelve C. cautus were tagged with acoustic tags and monitored for up to 579 days. Based on individuals detected within the receiver array for at least 2 months, C. cautus had small core (50% kernel utilization distribution, KUD) and home ranges (95% KUD) of 0·66 and 3·64 km2, respectively, and showed a strong habitat preference for mangroves, which are only found in the no‐take zone. This resulted in C. cautus spending most of their detected time within the no‐take zone boundaries (mean = 81·5%), showing that such a protected area could be beneficial to protect this species from extensive fishing pressure and local depletion, where required. Not all C. cautus remained within the acoustic array, however, suggesting that individual variations occur and that not all individuals would benefit from such protection. This study provides important information about the habitat, residency and movements of C. cautus that can be used for management and conservation. The strong affinity and residency of C. cautus within a mangrove‐fringing coastline, emphasizes the importance of mangrove habitat to the species and suggests that such preferences can be used to design appropriate no‐take zones for this species or others with similar habitat preferences.
Coastal populations of maritime countries in eastern Africa rely on fish as a primary source of protein, but baseline information on the abundance of fish communities on these coastlines is often ...lacking. We used baited remote underwater video stations to compare the abundance and diversity of reef fishes targeted by fishing at two sites in southern Mozambique, one at Lighthouse Reef within the Bazaruto Archipelago National Park and the other to the south at San Sebastian Reef on the San Sebastian Peninsula. Fish that are known targets of fisheries (mostly small-scale and artisanal) had an abundance that was almost three-times greater at San Sebastian Reef (80.22 ind. h
-1
SE 18.00) than at Lighthouse Reef (29.70 ind. h
-1
SE 8.91). Similarly, there was greater mean species richness at San Sebastian Reef (38.74 species h
-1
SE 2.79) than at Lighthouse Reef (25.37 species h
-1
SE 3.66). The main drivers of targeted fish abundance were habitat and depth, with shallow (<15 m) and mixed reef areas having the greatest abundance and richness. More sampling was done over sand habitat at Lighthouse Reef, which likely led to the lower abundance and species richness observed at this site; however, that finding could also be attributable to the fact that protection is provided to only a section of available coral reef habitat in a small area. Nevertheless, fish community structure was comparable between the sites, with similar proportions of carnivores (78-81%), herbivores (12-14%) and omnivores (7-8%). Our findings highlight the variation in species abundance and assemblages of coral-reef fish targeted by fishing in Mozambique and emphasise the importance of localised environmental variables as a driver of these patterns. To ensure maximum protection of Lighthouse Reef fish communities, we recommend an extension of the no-take zone to include the entire reef complex.
This study recorded the scarring rate and severity for whale sharks Rhincodon typus from three Indian Ocean aggregations (Australia, Seychelles and Mozambique), and examined whether scarring (mostly ...attributed to boat strikes and predator attacks) influences apparent survival rates using photo‐identification libraries. Identifications were based on spot‐and‐stripe patterns that are unique to individual whale sharks. Scarring was most prevalent in the Seychelles aggregation (67% of individuals). Predator bites were the most frequent source of scarring (aside from minor nicks and abrasions) and 27% of individuals had scars consistent with predator attacks. A similar proportion of whale sharks had blunt trauma, laceration and amputation scars, the majority of which appeared to be caused by ship collisions. Predator bites were more common (44% of individuals) and scars from ship collisions were less common at Ningaloo Reef than at the other two locations (probability of among‐site differences occurring randomly = 0·0007 based on a randomized multinomial contingency analysis). In all aggregations, scars occurred most often on the caudal fin, which may result from the fin being the body part closest to the surface when boats pass over, or they may provide a large target for predator attack. No evidence was found for an effect of scarring on apparent survival (φ; mean ±s.e.) for the Ningaloo (not scarred φ= 0·858 ± 0·033; scarred φ= 0·929 ± 0·033) or Seychelles populations (not scarred φ= 0·502 ± 0·060; scarred φ= 0·538 ± 0·070). The lower apparent survival of the Seychelles population may be attributed to a high number of transient whale sharks in this aggregation that might bias estimates. This study indicates that while scarring from natural predators and smaller vessels appears to be unrelated to whale shark survival, the effect of deaths related to ship strike need to be quantified to assist in future management of this species.
Genetic variation at the catechol-O-methyltransferase (COMT) gene has been significantly associated with risk for various neuropsychiatric conditions such as schizophrenia, panic disorder, bipolar ...disorders, anorexia nervosa and others. It has also been associated with nicotine dependence, sensitivity to pain and cognitive dysfunctions especially in schizophrenia. The non-synonymous single nucleotide polymorphism (SNP) in exon 4--Val108/158Met--is the most studied SNP at COMT and is the basis for most associations. It is not, however, the only variation in the gene; several haplotypes exist across the gene. Some studies indicate that the haplotypic combinations of alleles at the Val108/158Met SNP with those in the promoter region and in the 3'-untranslated region are responsible for the associations with disorders and not the non-synonymous SNP by itself. We have now studied DNA samples from 45 populations for 63 SNPs in a region of 172 kb across the region of 22q11.2 encompassing the COMT gene. We focused on 28 SNPs spanning the COMT-coding region and immediately flanking DNA, and found that the haplotypes are from diverse evolutionary lineages that could harbor as yet undetected variants with functional consequences. Future association studies should be based on SNPs that define the common haplotypes in the population(s) being studied.
Gilles de la Tourette syndrome (GTS) is characterized by multiple motor and phonic tics and high comorbidity rates with other neurobehavioral disorders. It is hypothesized that frontal-subcortical ...pathways and a complex genetic background are involved in the etiopathogenesis of the disorder. The genetic basis of GTS remains elusive. However, several genomic regions have been implicated. Among them, 17q25 appears to be of special interest, as suggested by various independent investigators. In the present study, we explored the possibility that 17q25 contributes to the genetic component of GTS. The initial scan of chromosome 17 performed on two large pedigrees provided a nonparametric LOD score of 2.41 near D17S928. Fine mapping with 17 additional microsatellite markers increased the peak to 2.61 (P=
.002). The original families, as well as two additional pedigrees, were genotyped for 25 single-nucleotide polymorphisms (SNPs), with a focus on three genes in the indicated region that could play a role in the development of GTS, on the basis of their function and expression profile. Multiple three-marker haplotypes spanning all three genes studied provided highly significant association results (P<
.001). An independent sample of 96 small families with one or two children affected with GTS was also studied. Of the 25 SNPs, 3 were associated with GTS at a statistically significant level. The transmission/disequilibrium test for a three-site haplotype moving window again provided multiple positive results. The background linkage disequilibrium (LD) of the region was studied in eight populations of European origin. A complicated pattern was revealed, with the pairwise tests producing unexpectedly high LD values at the telomeric
TBCD gene. In conclusion, our findings warrant the further investigation of 17q25 as a candidate susceptibility region for GTS.
Six extended dyslexic families with at least four affected individuals were genotyped with markers in three chromosomal regions: 6p23-p21.3, 15pter-qter, and 16pter-qter. Five theoretically derived ...phenotypes were used in the linkage analyses: (1) phonological awareness; (2) phonological decoding; (3) rapid automatized naming; (4) single-word reading; and (5) discrepancy between intelligence and reading performance, an empirically derived, commonly used phenotype. Two-point and multipoint allele-sharing analyses of chromosome 6 markers revealed significant evidence (P < 10(-6)) for linkage of the phonological awareness phenotype to five adjacent markers (D6S109, D6S461, D6S299, D6S464, and D6S306). The least compelling results were obtained with single-word reading. In contrast, with chromosome 15 markers, a LOD score of 3.15 was obtained for marker D15S143 at theta = 0.0 with single-word reading. Multipoint analyses with markers adjacent to D15S143 (D15S126, D15S132, D15S214, and D15S128) were positive, but none reached acceptable significance levels. Chromosome 15 analyses with the phonological awareness phenotype were negative. Parametric and nonparametric linkage analyses with chromosome 16 markers were negative. The most intriguing aspect of the current findings is that two very distinct reading-related phenotypes, reflecting different levels in the hierarchy of reading-related skills, each contributing to different processes, appear to be linked to two different chromosomal regions.
Global declines of shark populations are of concern because of their largely assumed role as moderators of ecosystem function. Without long-term data on movement patterns for many species, it is ...impossible to infer relative extinction risk, which varies as a function of range, dispersal and habitat specificity and use. The past 50 yr of research on coastal sharks has revealed common movement patterns among species. In the horizontal plane, measured home range size generally increases with body size. We demonstrate meta-analytically the effects of increasing body size and monitoring time on home range size. Changes in the extent of horizontal movement might arise from ontogeny, predator avoidance or environmental tolerances. In the vertical plane, movement patterns include oscillatory vertical displacement, surface swimming, diel vertical migration and swimming at depth. These vertical movements are often attributed to foraging or navigation, but have been quantified less than horizontal patterns. Habitat specificity is often correlated with environmental conditions such as depth, salinity, substratum, and in some cases, prey availability. Site fidelity is common in species that use nursery areas. However, fidelity to mating, pupping, feeding and natal sites has only been observed in a few species. To date, few studies have examined habitat partitioning, although some general patterns have emerged: habitats appear to be subdivided by benthos type, prey availability and depth. The conservation of coastal sharks can be facilitated in some cases by the use of marine protected areas, especially for coastal resident species using specific nursery, reproduction or feeding areas. Partial protected-area closures might be effective during aggregation or migration periods to protect older size classes, but these must be applied with other management strategies such as reduced fishing and size or bag limits to protect individuals throughout different life history phases. More long-term research on habitat use, migration patterns and habitat partitioning is essential for developing successful management initiatives for coastal shark populations.
Haplotypes consisting of the (CTG)
n
repeat, as well as several flanking markers at the myotonic dystrophy (DM) locus, were analyzed in normal individuals from 25 human populations (5 African, 2 ...Middle Eastern, 3 European, 6 East Asian, 3 Pacific/Australo-Melanesian, and 6 Amerindian) and in five nonhuman primate species. Non-African populations have a subset of the haplotype diversity present in Africa, as well as a shared pattern of allelic association. (CTG)
18–35 alleles (large normal) were observed only in northeastern African and non-African populations and exhibit strong linkage disequilibrium with three markers flanking the (CTG)
n
repeat. The pattern of haplotype diversity and linkage disequilibrium observed supports a recent African-origin model of modern human evolution and suggests that the original mutation event that gave rise to DM-causing alleles arose in a population ancestral to non-Africans prior to migration of modern humans out of Africa.
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