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Advances in the aquatic sciences
RESEARCH ARTICLE (Open Access)

‘Superbull’ males: what role do they play and what drives their appearance within the Doryteuthis gahi Patagonian Shelf population?

Jessica B. Jones https://orcid.org/0000-0003-3098-6811 A B C G , Graham J. Pierce A D E F , Paul Brickle A C , Zhanna N. Shcherbich B and Alexander I. Arkhipkin A B
+ Author Affiliations
- Author Affiliations

A School of Biological Sciences, University of Aberdeen, Zoology Building, Tillydrone Avenue, Aberdeen, AB24 2TZ, Scotland, UK.

B Fisheries Department, Falkland Islands Government, Stanley, PO Box 598, FIQQ 1ZZ, Falkland Islands.

C South Atlantic Environmental Research Institute, PO Box 609, Stanley Cottage, Stanley, FIQQ 1ZZ, Falkland Islands.

D Centro de Estudos do Ambiente e do Mar, Universidade de Aveiro, PT-3810-193 Aveiro, Portugal.

E Departamento de Biologia, Universidade de Aveiro, PT-3810-193 Aveiro, Portugal.

F Instituto de Investigacións Mariñas (Consejo Superior de Investigaciones Cientificas), Eduardo Cabello 6, E-36208 Vigo, Spain.

G Corresponding author. Email: jjones@fisheries.gov.fk

Marine and Freshwater Research 70(12) 1805-1817 https://doi.org/10.1071/MF18285
Submitted: 2 August 2018  Accepted: 1 February 2019   Published: 12 April 2019

Journal Compilation © CSIRO 2019 Open Access CC BY-NC-ND

Abstract

Cephalopod populations exhibit high variability in life history characteristics, such as longevity and size-at-age. The aim of this study was to understand how characteristics of a newly described ‘superbull’ male morph in Doryteuthis gahi populations (Patagonian Shelf) arise and whether there is a selective advantage. At the population level, it is speculated that superbulls provide temporal and spatial connectivity, but individual benefit is less obvious. Age structure and reproductive potential of males was investigated to determine whether superbulls could provide connectivity. Environmental variables affecting size-at-age were explored to ascertain whether morphological differences were primarily phenotypically driven. Superbulls from the autumn spawning cohort were significantly older than the residual population, with added longevity potentially leading to spawning with the following cohort. A reduction in relative testis weight was apparent in superbulls, but spermatophore production remained high. Generalised additive mixed models indicated temperature, location and hatch year had significant effects on size-at-age. Weak correlations between warm El Niño–Southern Oscillation phases and superbull abundance were found. The results suggest that superbulls provide temporal connectivity and arise through phenotypic plasticity, likely providing connectivity as a side effect of body shape and size rather than a genetically selected advantage.

Additional keywords: cephalopods, plasticity, population structure, reproduction, southwest Atlantic, statolith.


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