The story of cod fishing actually touches on many important aspects of the history pupils study.
Students could write their own story of a Viking voyage, beginning with a prompt such as "Thanks the gods for this salted fish..." and then go on to explain how and why it was so important. Inspiration for such writing might be found in Viking stories such as the Vinland sagas. Students might create a similar piece of writing, but with the emphasis on the importance of fish to the explorers of the period of the voyages of discovery. Fish as food, fish as profit motive, fish as food for slaves and in exchange for slaves - the possibilities are endless. Websites such as the Mersey Gateway (www.mersey-gateway.org.uk) contain documents such as letters and contracts showing humble fish (and other) merchants scrabbling to invest in slave-trading ventures. Another opportunity at KS3 is for students to investigate the North Sea fish trade in the medieval period, particularly from Hull. It is a useful reminder that Britain is very definitely not an island, in trade terms, even in this early period.
The attempts to preserve fish stocks could be a case study on international co-operation through UN or related agencies. The usual studies centre on political trouble-spots or civil wars, but preservation of natural resources might be a more attractive subject for some students.