Edward D. Farrell

Reproductive biology of the starry smooth-hound shark Mustelus asterias: geographic variation and implications for sustainable exploitation.

Examination of the reproductive biology of Mustelus asterias in the north-east Atlantic Ocean highlighted apparent geographical variation in maturity, fecundity and ovarian cycle between Atlantic and Mediterranean populations. The stretch total length (L(ST) ) and age at 50% maturity for Atlantic males and females were estimated at 78 cm L(ST) and 4-5 years and 87 cm L(ST) and 6 years, respectively. Size at maturity of females was considerably smaller than in Mediterranean specimens (96 cm L(ST) ). Ovarian fecundity ranged from eight to 27 oocytes and uterine fecundity from six to 18 embryos. The gestation period was c. 12 months, followed by a resting period of c. 12 months, resulting in a biennial cycle. Females stored sperm in the oviducal gland and, unlike Mediterranean specimens, no uterine compartments were observed in Atlantic specimens. This study reveals the existence of strong, possibly adaptive, divergence in life-history traits in an elasmobranch, whose northern populations may be more susceptible to overexploitation than previously believed.

The use of byssus threads by Mytilus edulis as an active defence against Nucella lapillus

To assess whether Mytilus edulis is selective in its secretion of byssus threads and entrapment of gastropods, experiments were conducted in laboratory aquaria and in the field. Exposure to dogwhelks ( Nucella lapillus ) or their effluent induced mussels to produce twice as many byssus threads as mussels exposed only to winkles ( Littorina littorea ) or those exposed only to seawater. There were no significant differences among treatments in the area over which byssus threads were secreted. Significantly more byssus threads were attached to the shells of dogwhelks than to winkles. Laboratory experiments produced broadly similar results to those in the field, but the level of response in the laboratory was greater. It is concluded that byssus threads were attached selectively to dogwhelks and that they may serve as a defence against predation.

A Novel Method of Microsatellite Genotyping-By-Sequencing Using Individual Combinatorial Barcoding

This study examines the potential of next-generation sequencing based ‘genotyping-by-sequencing’ (GBS) of microsatellite loci for rapid and cost-effective genotyping in large-scale population genetic studies. The recovery of individual genotypes from large sequence pools was achieved by PCR-incorporated combinatorial barcoding using universal primers. Three experimental conditions were employed to explore the possibility of using this approach with existing and novel multiplex marker panels and weighted amplicon mixture. The GBS approach was validated against microsatellite data generated by capillary electrophoresis. GBS allows access to the underlying nucleotide sequences that can reveal homoplasy, even in large datasets and facilitates cross laboratory transfer. GBS of microsatellites, using individual combinatorial barcoding, is potentially faster and cheaper than current microsatellite approaches and offers better and more data.

Land-use legacies and soil development in semi-natural ecosystems in the marginal uplands of Ireland

Abstract The relationships between semi-natural oak woodlands and the podzolic nature of their soils were investigated at 14 wooded and nine non-wooded sites located in otherwise similar environments in Ireland Historical records and palynological data were used to evaluate vegetation-soil dynamics and land-use history for both site types. Wooded site podzols were found to have moror moder-like O horizons, a distinctive eluvial-illuvial sequence and were generally friable and deeply rooted. Non-wooded soils differed in having deeper, more fibrous Of horizons, E horizons with fragipan-like characteristics, and spodic B horizons frequently containing thin ironpans that restricted vertical rooting. There were appreciable amounts of mobile organically complexed and inorganic, poorly crystalline iron, especially in the spodic upper B horizons of most sites. This suggests that podzolisation was, and continues to be, a dominant process in virtually all the soils studied. Podzolisation may have been initiated by the presence of Pinus and episodic natural and/or anthropogenic fires. The Pinus climax occurred approximately 8000 years BP and this species persisted regionally to approximately 4000years BP. Though podzolisation is still the dominant soil process at the wooded sites, the presence of oak seems to retard podzolisation compared with non-wooded sites, where acidophilous species such as Calluna vulgaris dominate.

Diversity of demersal and megafaunal assemblages inhabiting sandbanks of the Irish Sea

Sandbanks are marine habitats of conservation importance under the EU Habitats Directive. These habitats are becoming subject to impacts of several human activities including fishing, aggregation extraction, and construction of offshore wind farms that may have detrimental effects on their structure and functioning. We characterised and compared the diversity and biological traits of demersal fish and megafaunal invertebrate assemblages inhabiting three sandbanks, one in the vicinity of a small existing wind farm and two which are proposed sites for future wind farm installations. Samples in the vicinity of the offshore wind farm were compared with two control sites on the same sandbank. There were significant differences in mean number of taxa, abundance and structure of assemblages between sandbanks. However, biological traits analyses (BTA) showed no differences in the functional traits of assemblages among sandbanks, suggesting functional redundancy. Despite a significant spatial variation in structure and Shannon diversity of assemblages between sites within sandbanks, fish and megafaunal assemblage did not differ between sites near wind turbines and the controls. The natural spatial variability in the diversity and biological traits of demersal and megafaunal assemblages inhabiting this naturally highly disturbed environment is larger than any changes associated with the presence of the wind turbines. This study provides important baseline data against which potential future impacts of human activities can be tested.

Resolving the ambiguities in the identification of two smooth-hound sharks (Mustelus mustelus and Mustelus punctulatus) using genetics and morphology

Elasmobranch species are among the most threatened marine fish, and sound biological data for many of them are lacking. In this context, the smooth-hounds (Mustelus spp., Triakidae, Carcharhiniformes) represent an intriguing genus, being characterized by unclear and sometimes contrasting diagnostic traits. Here, we present new insights into the identification of two closely related species, M. mustelus and M. punctulatus. The use of three different molecular markers on a dataset of 588 specimens highlighted a genetic distinction between the two species. However, whereas microsatellites provided unambiguous results in all the samples, the other two markers were not able to assign a fraction of the individuals (6.6% for cytochrome c oxidase subunit 1, 14.4% for Internal Transcribed Spacer 2), suggesting the occurrence of heteroplasmy and introgression due to past hybridisation events. The comparison between morphological traits, previously suggested as diagnostic for species identification, and genetic identification, enabled validation of the most reliable and practical morphological traits for species identification. The shape of the dermal denticles represents the most reliable trait, but its use during fieldwork may be impractical. The black spots on body sides were present almost exclusively in M. punctulatus, allowing its identification; however, their absence is not diagnostic for M. mustelus. The distance of the nostrils and the shape of the mouth are useful to distinguish the two species during fieldwork. Our results will allow an accurate identification of the two species leading to the collection of reliable data on their distribution, life history traits, exploitation and status of conservation.

Seasonal migration of the starry smooth-hound shark Mustelus asterias as revealed from tag-recapture data of an angler-led tagging programme.

The primary aim of this long-term angler-led tagging programme was to gain information about seasonal changes in distribution of the starry smooth-hound shark Mustelus asterias, along the Dutch coast for management and conservation purposes. Between 2011 and 2014, M. asterias comprised 92·6% (n = 2418) of the total elasmobranch catch (n = 2612) by the licenced group of taggers within the Dutch Delta of which 2244 M. asterias were fin-tagged with plastic rototags. Sex and total length (LT ) composition inside the eastern tidal basin (Oosterschelde) were significantly different, i.e. more females and larger individuals, than outside indicating a pupping ground, which was confirmed by the capture of 30 newborn pups (≤32 cm). The distribution pattern of reported recaptured M. asterias (return-rate 3·6%, n = 80) showed a circannual migration between summering in the southern North Sea and wintering in the English Channel and the Bay of Biscay, and suggests that M. asterias is philopatric. The Dutch angling season for M. asterias runs from approximately mid-May to mid-October when the water temperature is above 13° C. Recaptures of eight mature females, but no males in the Bay of Biscay, indicate partial spatial segregation by sex, where mature females migrate over larger distances than immature females and males. These observations, with the absence of recaptures in other known summering areas (i.e. the Irish Sea and Bristol Channel), suggest that the southern North Sea is used by a separate population. Implications for management and recommendations to improve and expand the study approach are discussed.

Biological data from a data‐deficient shark: the Arabian smoothhound Mustelus mosis (Carcharhiniformes: Triakidae)

The present study provides information on length distribution, reproductive biology and diet of Mustelus mosis based on individuals caught in waters off the eastern Arabian Peninsula. Although ageing of vertebral centra was attempted, band pairs were of low clarity and counts could not be confidently assigned.