Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ukma!husc6!yale!Ram-Ashwin
From: Ram-Ashwin@cs.yale.edu (Ashwin Ram)
Newsgroups: sci.bio
Subject: How do fish know how large to grow?
Keywords: fish size
Message-ID: <59420@yale-celray.yale.UUCP>
Date: 4 May 89 14:46:29 GMT
Sender: root@yale.UUCP
Reply-To: Ram-Ashwin@cs.yale.edu (Ashwin Ram)
Followup-To: sci.bio,alt.aquaria
Organization: Computer Science, Yale University, New Haven, CT 06520-2158
Lines: 25

The size that a fish will grow to depends in some bizarre manner on the size of
the tank it's kept in.  Fish grow larger in larger tanks, and reach their
maximum size only in very large tanks or in the wild.  It's as if there was some
kind of invisible "pressure" from the tank that restricts the growth of the
fish.  Anyone have a real explanation?  How does the fish "know" how large to
grow?

I heard a rumor that the fish release some chemical which restricts their growth
rate.  In an unrestricted environment, this is of no consequence since it is
dispersed into minute concentrations, in a large tank this is less true and in a
small tank the concentration is high.  Is this true, and if so, what is this
mystery chemical?  A hormone?  Is its concentration affected by the presence of
other fish in the same tank (i.e., do all fish release similar chemicals)?

Whatever the mechanism, is a fish's size dependent only on the size of the tank,
or on the presence of other fish in the same tank?

-- Ashwin.

ARPA:    Ram-Ashwin@cs.yale.edu
UUCP:    {decvax,ucbvax,harvard,cmcl2,...}!yale!Ram-Ashwin
BITNET:  Ram@yalecs

P.S. Please follow up to alt.aquaria (where I first posted this question) in
addition to sci.bio.  Thanks.