If you want to choose a fishy cipher by Bruce et al, I'd go for Twofish.

Reason:

• Blowfish is not recommended anymore because of the small block size of 64 bits, among others. Even Bruce is not recommending it anymore - it's an old but unbroken cipher;
• Twofish is a relatively modern 128 bit block cipher which is a drop in for AES - for the simple reason that it was designed to be AES;
• Threefish is mainly used as tweakable block size construction within the Skein hash function; it is not well defined as a block cipher, and has a large block size and high number of rounds;
• Dopefish is actually not a block cipher but a character in Commander Keen.

Threefish is too specialized and not explicitly defined for block cipher modes of operation. Furthermore, Threefish has a block size different from AES candidates (256 or even 512 bits instead of 128). This makes it less likely that you will find it in many cryptographic libraries and makes it harder to switch to / from other AES candidates or, indeed, AES.

Blowfish and Dopefish are right out, leaving Twofish.

If you want to choose a fishy cipher by Bruce et al, I'd go for Twofish.

Reason:

• Blowfish is not recommended anymore because of the small block size of 64 bits, among others. Even Bruce is not recommending it anymore - it's an old but unbroken cipher;
• Twofish is a relatively modern 128 bit block cipher which is a drop in for AES - for the simple reason that it was designed to be AES;
• Threefish is mainly used as tweakable block cipher construction within the Skein hash function; it has a large block size and high number of (relatively simple) rounds;
• Dopefish is actually not a block cipher but a character in Commander Keen.

Threefish is too specialized and not explicitly defined for block cipher modes of operation. Furthermore, Threefish has a block size different from AES candidates (256 or even 512 bits instead of 128). This makes it less likely that you will find it in many cryptographic libraries and makes it harder to switch to / from other AES candidates or AES itself.

The fact that it is tweakable and has a large block size may make Threefish more applicable for state-of-the art schemes - but I don't think that's what you're are after.

Blowfish and Dopefish are right out, leaving Twofish.

If you want to choose a fishy cipher by Bruce et al, I'd go for Twofish.

Reason:

• Blowfish is not recommended anymore because of the small block size of 64 bits, among others. Even Bruce is not recommending it anymore - it's an old but unbroken cipher;
• Twofish is a relatively modern 128 bit block cipher which is a drop in for AES - for the simple reason that it was designed to be AES;
• Threefish is mainly used as tweakable block size construction within the Skein hash function; it is not well defined as a block cipher, and has a large block size and high number of rounds;
• Dopefish is actually not a block cipher but a character in Commander Keen.

So Blowfish is not recommended anymore, Threefish is too specialized and not explicitly defined for block cipher modes of operation. Furthermore, Threefish has a block size different from AES candidates (256 bits instead of 128). This makes it less likely that you will find it in many cryptographic libraries and makes it harder to switch to / from other AES candidates or, indeed, AES.

Dopefish is right out, leaving Twofish.

If you want to choose a fishy cipher by Bruce et al, I'd go for Twofish.

Reason:

• Blowfish is not recommended anymore because of the small block size of 64 bits, among others. Even Bruce is not recommending it anymore - it's an old but unbroken cipher;
• Twofish is a relatively modern 128 bit block cipher which is a drop in for AES - for the simple reason that it was designed to be AES;
• Threefish is mainly used as tweakable block size construction within the Skein hash function; it is not well defined as a block cipher, and has a large block size and high number of rounds;
• Dopefish is actually not a block cipher but a character in Commander Keen.

Threefish is too specialized and not explicitly defined for block cipher modes of operation. Furthermore, Threefish has a block size different from AES candidates (256 or even 512 bits instead of 128). This makes it less likely that you will find it in many cryptographic libraries and makes it harder to switch to / from other AES candidates or, indeed, AES.

Blowfish and Dopefish are right out, leaving Twofish.