Transatlantic stock mixing in basking sharks Cetorhinus maximus is supported by low genetic diversity in populations throughout the Atlantic Ocean. However, despite significant focus on the species' ...movements; >1500 individual sharks marked for recapture and >150 individuals equipped with remote tracking tags, only a single record of transatlantic movment has been previously recorded. Within this context, the seredipitous re‐sighting of a female basking shark fitted with a satellite transmitter at Malin Head, Ireland 993 days later at Cape Cod, USA is noteworthy.
Two techniques are described to calculate energy densities for the bell, gonad and oral arm tissues of three scyphozoan jellyfish (
Cyanea capillata,
Rhizostoma octopus and
Chrysaora hysoscella). ...First, bomb-calorimetry was used, a technique that is readily available and inexpensive. However, the reliability of this technique for gelatinous material is contentious. Second, further analysis involving the more labour intensive proximate-composition analysis (protein, fat and carbohydrate) was carried out on two species (
C. capillata and
R. octopus). These proximate data were subsequently converted to energy densities. The two techniques (bomb-calorimetry and proximate-composition) gave very similar estimates of energy density. Differences in energy density were found both amongst different species and between different tissues of the same species. Mean (±
S.D.) energy density estimates for whole animals from bomb-calorimetry were 0.18
±
0.05, 0.11
±
0.04, and 0.10
±
0.03 kJ g wet mass
−
1
for
C. capillata,
R. octopus, and
C. hysoscella respectively. The implications of these low energy densities for species feeding on jellyfish are discussed.
Infrequent and exceptional behaviours can provide insight into the ecology and physiology of a particular species. Here we examined extraordinarily deep (300-1250 m) and protracted (>1h) dives made ...by critically endangered leatherback turtles (Dermochelys coriacea) in the context of three previously suggested hypotheses: predator evasion, thermoregulation and exploration for gelatinous prey. Data were obtained via satellite relay data loggers attached to adult turtles at nesting beaches (N=11) and temperate foraging grounds (N=2), constituting a combined tracking period of 9.6 years (N=26,146 dives) and spanning the entire North Atlantic Ocean. Of the dives, 99.6% (N=26,051) were to depths <300 m with only 0.4% (N=95) extending to greater depths (subsequently termed ;deep dives'). Analysis suggested that deep dives: (1) were normally distributed around midday; (2) may exceed the inferred aerobic dive limit for the species; (3) displayed slow vertical descent rates and protracted durations; (4) were much deeper than the thermocline; and (5) occurred predominantly during transit, yet ceased once seasonal residence on foraging grounds began. These findings support the hypothesis that deep dives are periodically employed to survey the water column for diurnally descending gelatinous prey. If a suitable patch is encountered then the turtle may cease transit and remain within that area, waiting for prey to approach the surface at night. If unsuccessful, then migration may continue until a more suitable site is encountered. Additional studies using a meta-analytical approach are nonetheless recommended to further resolve this matter.
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•The interactions of diverse microbes with Fusarium differ both qualitatively and quantitatively.•Key parameters that determine efficacy of fungal inhibition were identified.•A simple ...inhibition coefficient was developed to quantify antifungal activity.•This inhibition coefficient was consistent with potency of known biocontrol agents.
Microbial interactions depend on a range of biotic and environmental variables, and are both dynamic and unpredictable. For some purposes, and under defined conditions, it is nevertheless imperative to evaluate the inhibitory efficacy of microbes, such as those with potential as biocontrol agents. We selected six, phylogenetically diverse microbes to determine their ability to inhibit the ascomycete Fusarium coeruleum, a soil-dwelling pathogen of potato tubers that causes the storage disease dry rot. Interaction assays, where colony development was quantified (for both fungal pathogen and potential control agents), were therefore carried out on solid media. The key parameters that contributed to, and were indicative of, inhibitory efficacy were identified as: fungal growth-rates (i) prior to contact with the biocontrol agent and (ii) if/once contact with the biocontrol agent was established (i.e. in the zone of mixed culture), and (iii) the ultimate distance traveled by the fungal mycelium. It was clear that there was no correlation between zones of fungal inhibition and the overall reduction in the extent of fungal colony development. An inhibition coefficient was devised which incorporated the potential contributions of distal inhibition of fungal growth-rate; prevention of mycelium development in the vicinity of the biocontrol agent; and ability to inhibit plant-pathogen growth-rate in the zone of mixed culture (in a ratio of 2:2:1). The values derived were 84.2 for Bacillus subtilis (QST 713), 74.0 for Bacillus sp. (JC12GB42), 30.7 for Pichia anomala (J121), 19.3 for Pantoea agglomerans (JC12GB34), 13.9 for Pantoea sp. (S09:T:12), and −21.9 (indicating a promotion of fungal growth) for bacterial strain (JC12GB54). This inhibition coefficient, with a theoretical maximum of 100, was consistent with the extent of F. coeruleum-colony development (i.e. area, in cm2) and assays of these biocontrol agents carried out previously against Fusarium spp., and other fungi. These findings are discussed in relation to the dynamics and inherent complexity of natural ecosystems, and the need to adapt models for use under specific sets of conditions.
Indoles, including 5-methoxy-2-methyl-indole (5MeO2MeIn), are a potent trigger of strobilation in jellyfish polyps. Indoles may be an alternative method to cooling to induce strobilation, but the ...ephyrae produced should have similar or better rates of survival, deformities, growth, and behaviour to those produced by cooling, and polyps should remain viable after strobilating. We used two experiments to optimise the use of 5MeO2MeIn to induce strobilation in
Aurelia coerulea
(Scyphozoa). First, we compared rates of strobilation, survival, and deformities of ephyrae and budding of polyps exposed to 1.25, 2.5, and 5.0 µM 5MeO2MeIn for 3 days to cooling at 14 °C. Polyps in the indole and cooled treatments strobilated after 10 days and produced similar numbers of ephyrae, but more ephyrae were deformed in the 5.0 µM treatment and survival of ephyrae was lower in the 2.5 and 5.0 µM treatments than the cooled treatment. Polyps exposed to all three concentrations of indoles failed to bud or died after strobilation. Next, we exposed polyps to 0.7, 1.25, and 2.5 µM 5MeO2MeIn for four hours. Polyps exposed to all indole concentrations strobilated and produced similar numbers of ephyrae, but more ephyrae were deformed in the 2.5 µM treatment. Survival, behaviour, and sizes of ephyrae were similar 7 and 14 days after strobilation (although ephyrae pulsed faster in the 1.25 µM treatment at 14 days) and budding rates were similar in the indole and cooled treatments. Thus, exposing polyps to 0.7–1.25 µM 5MeO2MeIn for 4 h is a viable and efficient alternative to cooling to induce strobilation in polyps.
The overall extent of habitat use by leatherback turtles in the North Atlantic, and hence their possible interactions with longline fisheries, is unknown. Here we use long-term satellite telemetry to ...reveal that leatherbacks range throughout the North Atlantic, indicating that closing limited areas to longline fisheries will probably have only partial success in reducing turtle bycatch. Although turtles dive very deeply on occasion (one descended to a maximum depth of 1,230 metres, which represents the deepest dive ever recorded for a reptile), they generally restrict their diving to less than 250 metres, which increases the chance that they will encounter longline hooks.
Abstract
Porbeagles throughout the North Atlantic have experienced severe population decline through overfishing, with the northeastern population listed as critically endangered. Management of this ...population is constrained by the paucity of data on porbeagle population structure, distribution and behaviour in this region. Here we use a long-term (47 year) Irish capture-mark-recapture dataset to investigate the population structure, spatial distribution and seasonal movements of this species. From 1970–2017, a total of 268 sharks (9 recaptures) were ID tagged, with most individuals likely being juvenile based on length at maturity estimates (mean total length = 143.9 cm, SD = 35.4). Almost all captures were recorded at three distinct locations near angling hubs along the south, west and north coasts with catches peaking in August. Long-term trends in capture date indicated a shift towards earlier capture dates in the northern site (n = 153). Our findings suggest Irish waters may act as a persistent summer aggregation site for juveniles, which show evidence for seasonal site fidelity, returning to nearby locations between years. These findings demonstrate the utility of such programmes, which can be implemented, with minimal expense by engaging with the angling sector, to elucidate the population structure and distribution of wide-ranging fish species.
Jellyfish are increasingly topical within studies of marine food webs. Stable isotope analysis represents a valuable technique to unravel the complex trophic role of these long-overlooked species. In ...other taxa, sample preservation has been shown to alter the isotopic values of species under consideration, potentially leading to misinterpretation of trophic ecology. To identify potential preservation effects in jellyfish, we collected
Aurelia aurita
from Strangford Lough (54
o
22′44.73″N, 5
o
32′53.44″W) during May 2009 and processed them using three different methods prior to isotopic analysis (unpreserved, frozen and preserved in ethanol). A distinct preservation effect was found on δ
15
N values: furthermore, preservation also influenced the positive allometric relationship between individual size and δ
15
N values. Conversely, δ
13
C values remained consistent between the three preservation methods, conflicting with previous findings for other invertebrate, fish and mammalian species. These findings have implications for incorporation of jellyfish into marine food webs and remote sampling regimes where preservation of samples is unavoidable.
Seabirds are central place foragers during the breeding season and, as marine food resources are often patchily distributed, flexibility in foraging behaviour may be important in maintaining prey ...delivery rates to chicks. We developed a methodological approach using a combination of GPS data loggers and temperature-depth recorders that allowed us to describe the behaviour of surface-feeding seabirds. Specifically, we tested whether differences in foraging behaviour of black-legged kittiwakesRissa tridactylacould be linked with reproductive success by comparing 2 consecutive years at 2 sites. At Rathlin Island (Northern Ireland) during 2010, foraging differed markedly from that during 2009 and from that at Lambay Island (Republic of Ireland) during both years. Birds exhibited foraging trips of greater duration, travelled a greater total distance, spent more time in transit and spent longer recuperating on the surface of the water. This notable shift was associated with a decline in breeding success, with greater loss of eggs to predation and lower prey delivery rates, resulting in the starvation of 15% of chicks. We suggest that food resources were reduced or geographically less accessible during 2010, with suitable foraging areas located further from the colony. Birds did not invest greater amounts of time attempting to catch prey. Thus, our results indicate that kittiwakes at Rathlin modulated their foraging behaviour not by increasing foraging effort through feeding more intensively within prey patches but by extending their range to increase the probability of encountering more profitable prey patches.
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