INTRODUCTION. 



When commencing to investigate fish and fisheries, it- naturally first occurs 

 to the inquirer to ask what is a fish ? at what geological epoch of time did it 

 first leave a trace of its existence on the surface of the globe we inhabit ? 

 how does it live, move, and continue its kind ? 



In a work like the present, a small space only can be given to some of 

 these various questions, and I have deemed it. best to abbreviate remarks 

 upon embryology, comparative anatomy and physiology, as well as the 

 numerous and diversified systems of classification (referriug the reader to the 

 • various treatises on these subjects) in order to dwell more particularly upon 

 facts that come especially to the notice of the field-naturalist, fish-culturist 

 and fisherman. 



For practical purposes it is highly desirable to endeavour to ascertain what 

 are the geographical limits within which the various forms of fish life are 

 found, should the species be migratory, the causes of their migrations, and 

 how such are dependent on ocean circulation, currents, seasons, temperature, 

 food, or the necessity for the continuation of their kind. ' Why is it that 

 some forms flourish and increase while others dwindle away and decrease ; 

 what are the effects of light or darkness, depths or the varied physical con- 

 ditions of the waters in which they reside ? Likewise how fish are affected 

 by storms and electrical disturbances, or in short what are their enemies or 

 their friends, and conditions tending towards the perpetuation or extermina- 

 tion of their race ? 



When inquiring into what is their favourite food, we have to remember 

 that in selecting such they must be guided by the faculties of sight,- taste, or 

 sun II, perhaps assisted by touch, and possibly by sound, and this leads on 

 to the consideration of . respiration and digestion. Fishes likewise possess 

 emotions and instincts, sensibility to pain or 'the reverse, modifications of 

 form sometimes due to age or sex, and alterations of. colour consequent uppn 

 the nuptial season, external relationship or disease. 



Some residing at great depths or in dark caverns have their eyes deficient, 

 others in the abysses of the ocean possess them enormously developed in 

 order to utilize every ray of light, while a few likewise living in apparently 



