Atlantic Cod

A Bio-Ecology

George A. Rose, George A. Rose

• Publisher: Wiley-Blackwell
• Year: 2018
• ISBN:
  9781119460671
• Edition: 1
• Topic: Technik & Maschinenbau
• Subtopic: Fischerei & Aquakultur

A comprehensive handbook, covering all aspects of the Atlantic cod including the biology, ecology, life histories, behaviour, commercial exploitation and conservation

Not only is Atlantic cod one of the most valuable food fish in the world's oceans, it is an important component of North Atlantic ecosystems and has been subject to much research into its biology, ecology and exploitation. After hundreds of years of exploitation, overfishing in the last half of the 20 th Century caused many stocks to collapse, most famously the Northern cod stock off Newfoundland and Labrador, Canada. Since then, most cod stocks have been better researched and managed, but remain in a variety of states, from fully recovered to continued decline. This book, written by world experts, describes that research and management, and the importance of cod and its fisheries on North Atlantic cultures and economies, with impacts well beyond the range of the species.

Atlantic Cod: Bio-Ecology of the Fish offers insightful chapter coverage of cod nomenclature, taxonomy, phylogeny and morphology; physiology and ecophysiology; reproduction and spawning behavior; early life history and pre-recruitment processes; migrations, movements and stock identity; feeding, growth and energetics; the place of cod in the ecosystem; the exploitation of cod through history and present day commercial fisheries and precautionary management for sustainable fisheries; impacts of climate change on cod biology and ecology; and the future of the species and its fisheries.

• Discusses the major commercial importance of Atlantic cod through history
• Provides a comprehensive treatment of the bio-ecology of the most researched and highly exploited fully marine species
• Examines how the decline (and recovery) of cod stocks is of great political and scientific interest
• An essential purchase for marine fisheries scientists

Atlantic Cod: Bio-Ecology of the Fish is a vital book for all fisheries scientists, managers and fish biologists.

1
Atlantic Cod: Origin and Evolution

Guðrún Marteinsdóttir¹ and George A. Rose²

¹Institute of Life and Environmental Sciences, University of Iceland, Reykjavik, Iceland

²Institute for the Oceans and Fisheries, University of British Columbia, Vancouver, British Columbia, Canada

Gadidae proper is virtually unique among fishes in having its headquarters on the continental shelf of the temperate North Atlantic … a region with a fish fauna comprised chiefly of the tag ends of groups having their main centers of diversity farther to the south or in the temperate North Pacific

Marshall and Cohen, 1973

The hero, Gadus morhua … is built to survive. Fecund, impervious to disease and cold … it was the perfect commercial fish

Mark Kurlansky, 1997

1.1 Introduction

The Atlantic cod ( Gadus morhua ) is one of the best‐known fishes of the world. It has none of the cachet of the Atlantic salmon ( Salmo salar ), nor the pure majesty of the Bluefin Tuna ( Thunnus thynnus ), nor the terrifying awe of the Great White Shark ( Carcharodon carcharias ), but alone among fishes, cod did indeed ‘change the world’ (Kurlansky 1997). It is a fish for all seasons and all people. Over the past millennium, the humble cod has fuelled economies and exploration, been fought over in a multitude of wars, changed history, and fed millions. No other fish, or indeed, any animal, can claim this. And despite 100 years of scientific research, the biology and behaviour of this species continues to surprise researchers and amaze human observers.

The Atlantic cod fisheries in Norway and the North and Baltic Seas have long and well‐known histories, and the role of the cod in the settlement and development of Iceland and Newfoundland is also well established, the latter having been described as a ‘great ship moored near the fishing banks’ (Harris et al. 1990). Less well known is how the cod fishery jump‐started the economy of Massachusetts and much of the New England colonies, now one of the most prosperous regions of the world. To this day, centre stage in the Massachusetts State House, still hangs the ‘sacred cod’.

The Atlantic cod is indeed a sacred fish over much of its range in the North Atlantic (Rose 2007). It has many names, in many languages and dialects, but almost everywhere, as with deities, it is seldom referred to directly. Most often it is simply fish, or fiskr, or variations of that ancient name.¹

Cod is not just a fish, it is the fish (Figure 1.1).

Figure 1.1 The fish – the Atlantic cod – here the yellow‐dark with white belly colour phase.

Figure 1.2 Cod aggregation at a spawning location in Þistilfjörður, North of Iceland. Spawning at this location often takes place at low temperatures (<3 °C; Thorsteinsson, personal communication). Photo Erlendur Bogason.

1.2 Taxonomy and Morphology

The Atlantic cod takes its scientific name, Gadus morhua , from the Greek gados, meaning fish, and the Latin morua, for cod. The species is a member of the family Gadidae of the order Gadiformes and superorder Paracanthopterygii. The Gadidae family includes 13 genera and 24 species, of which the genus Gadus contains only three (maybe four) species, the Atlantic cod, Pacific walleye pollock ( Gadus chalcogrammus ) and Pacific cod ( Gadus macrocephalus ) (Coulson et al. 2006).² It is still uncertain if the Greenland or Rock cod ( Gadus ogac ) is the same species as Pacific cod, or a very close relative. In coastal waters of Newfoundland and Labrador and Greenland, Atlantic and Greenland cod live in close proximity (Knickle and Rose 2014a,b). Other close‐living relatives in the Gadidae family include pouts, poutings and poor cod (Trisopterus species), saffron cod (Microgadus species and Eleginus navaga ), haddock ( Melanogrammus aeglefinus ), Atlantic pollock or saithe ( Pollachius virens ), whiting ( Merlangius merlangus ) and the sister species the polar cod (Boreogadus) and Arctic cod (Arctogadus) that are endemic to the Arctic (Carr et al. 1999; Coulson et al. 2006).

Atlantic cod and its relatives are distinguished by the presence of three dorsal fins on the back, two anal fins on the lower side and anteriorly located pelvic fins positioned slightly in front of the pectorals. The pelvic fins stand high on the body, a characteristic of all Paracanthopterygii. A distinguishing feature of the cod and some relatives is a barbel positioned at the end of the chin. Cod vary in colour depending on location, diet and immediate environment (Gosse and Wroblewski 2004; Sherwood and Grabowski 2010). The two main phases of coloration vary from grey‐green‐yellow to red‐brown, but other variations also occur.

1.3 Origin and Evolution

Atlantic cod adapted to occupy most all of the continental shelves that circumscribe the North Atlantic boreal region. These extensive continental shelves resulted from plate tectonics and the formation of the Atlantic Ocean that began some 150–200 million years ago (MYA) with...