In fish, sand will be pumped out of the mouth through the gill slit.
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The broad, triangular pectoral fins originate at or slightly before the level of the fifth gill slit.
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Cod have a distinct white lateral line running from the gill slit above the pectoral fin, to the base of the caudal or tail fin.
From the en.wikipedia.org
The indirect route of this nerve is the result of evolution of mammals from fish, which had no neck and had a relatively short nerve that innervated one gill slit and passed near the gill arch.