Collins M.A.,GSGSSI |
Laptikhovsky V.,FIPASS |
Strugnell J.M.,University of Cambridge
Journal of the Marine Biological Association of the United Kingdom | Year: 2010
Opisthoteuthis hardyi was originally described from a single male specimen caught near Shag Rocks (north-west of South Georgia) and no further specimens have been attributed to this species. During research fishing on the Patagonian slope to the south-east of the Falkland Islands 33 specimens of Opisthoteuthis were caught at depths ranging from 630 to 1391m. Morphological measurements indicated that these specimens were conspecific to the holotype of O. hardyi. The mitochondrial gene 16S rDNA was sequenced from two of these specimens and compared with a published sequence of the holotype and other Opisthoteuthidae to confirm the morphological data. This extends the geographical and bathymetric range of the species, which spans the Antarctic Polar Front. We also expand the original description, providing details of the digestive system and of the female reproductive system, with preliminary estimates of fecundity. Copyright © Marine Biological Association of the United Kingdom 2009.
Deep-Sea Research Part II: Topical Studies in Oceanography | Year: 2013
Long-term investigations of three abundant nektonic squid species from the Southwest Atlantic, Illex argentinus, Doryteuthis gahi and Onykia ingens, permitted to estimate important population parameters including individual growth rates, duration of ontogenetic phases and mortalities. Using production model, the productivity of squid populations at different phases of their life cycle was assessed and the amount of biomass they convey between marine ecosystems as a result of their ontogenetic migrations was quantified. It was found that squid are major nutrient vectors and play a key role as transient 'biological pumps' linking spatially distinct marine ecosystems. I. argentinus has the largest impact in all three ecosystems it encounters due to its high abundance and productivity. The variable nature of squid populations increases the vulnerability of these biological conveyers to overfishing and environmental change. Failure of these critical biological pathways may induce irreversible long-term consequences for biodiversity, resource abundance and spatial availability in the world ocean. © 2012 Elsevier Ltd.
Schuchert P.C.,FIPASS |
Arkhipkin A.I.,FIPASS |
Koenig A.E.,U.S. Geological Survey
Fisheries Research | Year: 2010
Trace element fingerprints of edge and core regions in otoliths from 260 specimens of Patagonian hoki, Macruronus magellanicus Lönnberg, 1907, were analyzed by LA-ICPMS to reveal whether this species forms one or more population units (stocks) in the Southern Oceans. Fish were caught on their spawning grounds in Chile and feeding grounds in Chile and the Falkland Islands. Univariate and multivariate analyses of trace element concentrations in the otolith edges, which relate to the adult life of fish, could not distinguish between Atlantic (Falkland) and Pacific (Chile) hoki. Cluster analyses of element concentrations in the otolith edges produced three different clusters in all sample areas indicating high mixture of the stocks. Cluster analysis of trace element concentrations in the otolith cores, relating to juvenile and larval life stages, produced two separate clusters mainly distinguished by 137Ba concentrations. The results suggest that Patagonian hoki is a highly mixed fish stock with at least two spawning grounds around South America. © 2009 Elsevier B.V.
McKeown N.J.,Aberystwyth University |
Arkhipkin A.I.,FIPASS |
Shaw P.W.,Aberystwyth University
Fisheries Research | Year: 2015
Information from genetic (microsatellites and mtDNA Control Region) and previously collected otolith (trace element fingerprinting of otolith core and edge) markers was jointly interpreted to describe dispersal and gene flow in the Patagonian hoki (Macruronus magellanicus), an intensively harvested marine fish with seasonal migrations between spawning and feeding grounds. Spawning adults from a Chilean (Pacific) spawning site and three feeding ground samples (one from Chile and two temporal samples from the Falkland Islands (Atlantic)) were analysed. The data indicated a high level of Atlantic/Pacific connectivity by means of non-natal homing of individuals to spawning aggregations. Against this background of regional connectivity however, genetic data support the existence of a reproductively isolated population within the overwintering stock. Otolith core results are compatible with reproductive isolation being effected by natal homing to an Atlantic spawning site and/or local adaptation. The discordance between geopolitically defined Atlantic and Pacific management stocks and underlying biocomplexity, and implications for sustainability, are discussed. The study highlights the importance of intraspecific variation in homing behaviours in shaping population structure and the merit of employing complementary analytical approaches. © 2014 Elsevier B.V.
Arkhipkin A.I.,FIPASS |
Journal of the Marine Biological Association of the United Kingdom | Year: 2012
The discovery thirty years ago of daily growth increments in squid statoliths and the development of statolith ageing techniques gave new insight into squid age, growth and metabolism. The techniques have shown that the majority of recent coleoid cephalopods live in the 'fast lane-, growing rapidly and completing their life cycles in a year or less. Surprisingly, these useful approaches to the study of age and growth in squid have not gained much momentum. Only approximately an eighth of more than 300 squid species have had their basic age assessed and described. Two dozen species are subject to continuing arguments about which increments to consider as daily growth increments. This paper outlines major problems encountered during age determination of squid and suggests ways to improve the techniques and make them applicable to a wider spectrum of species. © 2011 Marine Biological Association of the United Kingdom.