The life history and ecology of black scabbardfish (Aphanopus carbo Lowe 1839) in the north-east Atlantic

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dc.contributor.advisor Rogan, Emer en Ribeiro Santos, Ana 2013-12-05T15:40:52Z 2013 2013
dc.identifier.citation Ribeiro Santos, A. 2013. The life history and ecology of black scabbardfish (Aphanopus carbo Lowe 1839) in the north-east Atlantic. PhD Thesis, University College Cork. en
dc.identifier.endpage 208
dc.description.abstract The black scabbardfish is a deep water species that supports commercial fisheries across a large area of the NE Atlantic shelf. The life history of black scabbardfish is poorly understood and a major unresolved issue is population structure. In this study it was used a combination of methodologies to get further knowledge in the life history and population structure of A. carbo over its wide distribution range in the Northeast Atlantic. The new knowledge acquired during this study, will increase our ability to better manage this species in the NE Atlantic. It has been postulated that fish caught to the west of the British Isles are pre-adults that migrate further south (to Madeira) for spawning, implying a single panmictic population. In this study, specimens of Aphanopus carbo were sampled between September 2008 and May 2010 from two different areas: NW Scotland (French trawlers and deep water surveys) and Madeira Islands (longliners commercial landings). Geographical differences in reproductive state of scabbardfish were evident, supportive of a north-south migration theory. In the northern area, all specimens found were immature, while in Madeira all maturity stages were observed. In Madeira, spawning occurred during the fourth quarter, with peak maturity in October (males) and in November (females). The age of this species has proven difficult and has led to different and contradictory age and growth estimates. For this study, we used two reading interpretations to determine age and estimate the growth parameters. To the west of the British Isles, specimens reached a lower maximum age and had a higher growth rate than those caught off Madeira. These differences are consistent with the theory of a single population of black scabbardfish in the NE Atlantic, highly segregate, with smaller, immature and younger fish caught to the west of the British Isles and bigger and mature caught in Madeira Islands. The feeding ecology showed strong evidence that the diet of black scabbardfish is associated with the spawning migration of blue whiting, which may support a northerly feeding migration theory for black scabbardfish. The stable isotope analyses in the muscle of black scabbardfish identified that black scabbardfish feeds on species with epipelagic and benthopelagic affinities. Comparison with stable isotope analysis in Madeira samples indicated that black scabbardfish feed at a similar trophic level and has the same trophic niche width in both areas, assuming similar baseline isotope compositions. Otolith stable isotopes (oxygen - δ18O and nitrogen - δ15N) analyses were used as a tool to clarify migratory behaviour. Otolith isotope ratios can provide insight into whether adults caught around Madeira fed in an isotopically depleted northerly ecosystem (NW Scotland) during their pre-adult period and then migrate towards south to spawn. Overall, the results support a south-north migration of pre adult fish from spawning areas around Madeira and a north-south migration from the west of Scotland to the spawning areas. Given its life cycle there is an urgent need that the management process recognizes the existence of a continuous widely distributed stock of black scabbardfish between the west of the British Isles and Madeira. The results highlight large scale dispersal in this species which needs to be treated as a highly migratory species and be managed as a single population. en
dc.description.sponsorship Marine Institute (Sea Change strategy) en
dc.format.mimetype application/pdf en
dc.language.iso en en
dc.publisher University College Cork en
dc.rights © 2013, Ana Ribeiro Santos. en
dc.rights.uri en
dc.subject Black Scabbardfish en
dc.subject Northeast Atlantic en
dc.subject Reproductive dynamics en
dc.subject Age and growth en
dc.subject Trophic ecology en
dc.subject Population connectivity en
dc.subject.lcsh Deep-sea fisheries en
dc.subject.lcsh Trichiuridae en
dc.subject.lcsh Fisheries--Madeira (Madeira Islands) en
dc.subject.lcsh Fisheries--Scotland en
dc.subject.lcsh Marine fishes--Ecology en
dc.subject.lcsh Marine fishes--Age en
dc.title The life history and ecology of black scabbardfish (Aphanopus carbo Lowe 1839) in the north-east Atlantic en
dc.type Doctoral thesis en
dc.type.qualificationlevel Doctoral en
dc.type.qualificationname PhD (Science) en
dc.internal.availability Full text available en
dc.description.version Accepted Version
dc.contributor.funder Marine Institute en
dc.description.status Not peer reviewed en Biological, Earth & Environmental Sciences en
dc.check.reason This thesis is due for publication or the author is actively seeking to publish this material en
dc.check.opt-out Not applicable en
dc.thesis.opt-out false *
dc.check.chapterOfThesis Chapters of thesis - 3, 5, 6
dc.check.embargoformat E-thesis on CORA only en
ucc.workflow.supervisor *
dc.internal.conferring Autumn Conferring 2013 en

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© 2013, Ana Ribeiro Santos. Except where otherwise noted, this item's license is described as © 2013, Ana Ribeiro Santos.
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