A PLEA FOR OBSERVATION OF THE HABITS OF FISHES 

 AND AGAINST UNDUE GENERALIZATION. 



By THEODORE GILL, Pli. D., LL. D., 

 Honorary Associate in Zoology, Sinithsonian Institution. 



I have been requested to address the International Fishery Congress, but 

 on account of the extensive programme provided for it brevity will be recognized 

 as a virtue if not demanded as a requisite. I shall therefore confine my remarks 

 to a plea for the presentation of much wanted information respecting the habits 

 of fishes in general, but especially those which are the objects of pisciculture. 

 Indeed such knowledge is a necessary prerequisite for successful pisciculture and 

 should be made public in the interests of industry as well as of science. Never- 

 theless, essentials of some of our most esteemed fishes are scarcely known beyond 

 a very small circle of pisciculturists. The crappie of America (Pomoxis spa- 

 roides) is a notable case. It is one of our best fresh-water fishes, but the acces- 

 sible accounts of its habits are extremely meager and no account has been 

 published of its sexual intercourse, the preparation of a nest, or the care of the 

 eggs and young by the parent fish. 



Too mucn care can not be given to the detailed observation of the economy 

 of any fish, for differences between related species may exist which might be 

 least foreseen. For instance, two silurids occur in Europe which are so near 

 each other that they have been long nominally confounded; they are the com- 

 mon wels of central and eastern Europe and the glanis of Greece. Notwith- 

 standing their great morphological similarity, they differ remarkably in their 

 habits, for the wels takes no care of its eggs, while the male of the glanis exer- 

 cises paternal supervision for a prolonged period. Why the statement that the 

 two have been nominally confounded has been made will be explained later. 

 One more example of contrast may be cited. One of the best known and most 

 generally published accounts of parental care among fishes is that one, three 

 quarters of a century ago (1828), attributed to the hassars (Callichthys or Hoplo- 

 sternum) by Dr. John Hancock. Yet the species of a related genus (Corydoras) 

 have quite different habits in general as well as in courtship and oviposition; 



no care is exercised over the eggs by either parent. 



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