Oceanography and Marine Biology

An Annual Review: Volume 41

R. N. Gibson, R. J. A. Atkinson

• Publisher: CRC Press
• Year: 2003
• eBook ISBN: 9781134523078
• Edition: 1
• Topic: Biological Sciences
• Subtopic: Biology
• Index: Biological Sciences

Interest in oceanography and marine biology and its relevance to global environmental issues continues to increase, creating a demand for authoritative reviews that summarize recent research. Oceanography and Marine Biology: An Annual Review has catered to this demand since its foundation, by the late Harold Barnes, more than 40 years ago. It is an

Oceanography and Marine Biology: an Annual Review 2003, 41, 355–390
© R. N. Gibson and R. J. A. Atkinson, Editors
Taylor & Francis

THE DIET OF HARBOUR PORPOISE (PHOCOENA PHOCOENA) IN THE NORTHEAST ATLANTIC

M. B. SANTOS & G. J. PIERCE
Department of Zoology, University of Aberdeen, Tillydrone Avenue,
Aberdeen, AB24 2TZ, UK
e-mail: [email protected]

Abstract The harbour porpoise (Phocoena phocoena) is probably the most abundant small cetacean in the northeast Atlantic and as such is an important top predator. It is also one of the most threatened species, particularly as a consequence of fishery by-catch.

Porpoises feed mainly on small shoaling fishes from both demersal and pelagic habitats. Many prey items are probably taken on, or very close to, the sea bed. Even though a wide range of species has been recorded in the diet, porpoises in any one area tend to feed primarily on two to four main species (e.g. whiting (Merlangius merlangus) and sandeels (Ammodytidae) in Scottish waters).

Evidence for selective predation is equivocal. Many studies provide evidence of geographic, seasonal, interannual, ontogenetic or sexual differences in prey types or prey sizes, and such differences are often (speculatively) interpreted in terms of prey availability. A few studies demonstrate trends in diet selection that are consistent with changes in prey abundance. However, lack of availability of prey abundance data at an appropriate spatial and temporal scale is often a problem.

Porpoise diets overlap extensively with diets of other piscivorous marine predators (notably seals). Many of the main prey species are also taken by commercial fisheries, although porpoises tend to take smaller fishes than those targeted by fisheries. Given their high abundance, porpoises clearly remove substantial quantities of fish.

The literature on porpoise diets in the northeast Atlantic suggests that there has been a long-term shift from predation on clupeid fish (mainly herring Clupea harengus) to predation on sandeels and gadoid fish, possibly related to the decline in herring stocks since the mid-1960s. Evidence from studies on seals suggests that such a shift could have adverse health consequences.

Food consumption brings porpoises into contact with two important threats – persistent organic contaminants and fishing nets, both of which have potentially serious impacts.

Introduction

The harbour or common porpoise, Phocoena phocoena (Linnaeus 1758), is one of the six species recognised in the family Phocoenidae (Read 1999). Its common name, porpoise, derives from the Latin porcus piscus (= pigfish) and was used in Ancient Rome. Linnaeus (1758) distinguished it from the common dolphin by calling it Delphinus phocoena, from the Greek word phokia (= seal), due to its lack of beak and its seal-like appearance.

Harbour porpoises, one of the most common cetaceans in European waters (Watson 1985), are small with an average adult length of 150 cm to 160 cm and an average weight of 45kg to 60 kg (Gaskin et al. 1974). Maximum sizes of animals stranded in the UK have been reported as 163 cm and 54 kg in males and 189 cm and 81 kg in females (Lockyer 1995) although more recent work by Santos et al. (2001a) reported maximum sizes for males and females as 170 cm (55 kg) and 171 cm (55.5 kg), respectively, for porpoises stranded in Scotland. Harbour porpoises stranded in northwest Spain and Portugal seem to be larger, and several specimens have measured more than 200 cm (Donovan & Bjørge 1995, Sequeira 1996).

There is some variation in the maximum ages reported for different harbour porpoise populations: no porpoises over 17 yr of age have been found...

Table of contents

• Cover Page
• Title Page
• Copyright Page
• Preface
• Oxygen Minimum Zone Benthos: Adaptation and Community Response to Hypoxia
• Antarctic Marine Benthic Diversity
• Influence of Marine Allochthonous Input On Sandy Beach Communities
• The Effects of Sedimentation On Rocky Coast Assemblages
• Exotic Molluscs In the Mediterranean Basin: Current Status and Perspectives
• Detritus In the Epilithic Algal Matrix and Its Use By Coral Reef Fishes
• Ecology of Whale Falls At the Deep-Sea Floor
• The Diet of Harbour Porpoise (Phocoena Phocoena) In the Northeast Atlantic