NOTES ON FISHES OF THE DELAWARE RIVER. 833 



by their numbers — speciuieus varying from 1 inch to 10 — the rock-fish 

 must breed in the river or its principal tributaries, very generally. 



The largest rock-fish that 1 have accurate knowledge of^ taken in 

 the Delaware River, at Trenton, weighed 40 pounds; but I have no 

 measurements of the specimen. Fish from 2 to 5 pounds are not uncom- 

 mon; but specimens of greater weight, formerly abundant, are now only 

 occasionally met with, at least above Philadelphia. 



While it is well known that the rock-fish comes up the river from the 

 sea, and enters, as stated, the various tributary streams, there is some- 

 thing of a mystery connected with their movements in this respect. I 

 think there can be no doubt but that the usual time of spawning is in 

 June, and that many come from the bay (and ocean ?)in April and May 

 for that purpose ; but in August and September, when the thousands of 

 young shad are going seaward, there is such an increase in the numbers 

 of large fish that I am inclined to think many non-breeding fish come 

 up from salt water at this time to prey upon the young shad, or that 

 the rock-fish breed in tide-water and much to the south of Trenton, N. J. 



The favorite localities of these fish may be broadly stated to be in swift 

 currents of varying depth — the larger fish in the deeper waters. I have 

 never discovered that they exhibited any predilection for the neighbor- 

 hood of rocks, patches of grass, &c. A decided current and cool water 

 are the two essentials, and without them they soon perish. 



The food of the rock-fish consists exclusively of small fishes ; and it 

 is the pursuit of them into small streams that explains their presence 

 where one would hardly expect to find them. A rock-fish will fre- 

 quently "corner up" a small school of minnows, and then pick them 

 up as rapidly and with as great ease as a fowl will pick grains of 

 corn ; and while devouring the luckless minnows, will keep them in a 

 small space, close together, all the time. There is no cessation of this 

 murderous work while a fish remains ; for after devouring all that it is 

 possible for him to hold, a mere love of destruction keeps him at work. 

 I once had a very favorable opportunity of watching the rock-fish feed in 

 this way. It was a moderate-sized fish, about a foot long, and as near 

 as I could determine it devoured a dozen " cyprinellas " (silver-finned 

 minnows) in four minutes. If I err in my estimate if is on the safe side, 

 and it may be it was fifteen minnows in that length of time. 1 subse- 

 quently captured a dozen of these pretty shiners, and found I could by 

 no means squeeze them into a bulk that was not much larger than the 

 estimated interior of a rock-fish a foot in length ; and yet it is certain that 

 the minnows captured by the rock-fish were swallowed without decapi- 

 tation or other reduction of size, for in that case I should have seen the 

 fragments of the minnows floating in the clear waters. 



I have already expressed the opinion that the rock-fish spawns, in 

 Central New Jersey, about the 1st of June. This occurs in the tribu- 

 taries of the river, if not in the river itself. As yet I have not been 

 able to find them in the act of spawning, or oven the impregnated ova, 



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