While most caves can have exocrine, they are random. The ones marked with the fish are almost guaranteed to have exocrine.
Map edited from here

"These fish hatch out of translucent pods formed in caverns below the Infested landscape. They hover to feed."

Catching info

Cycle: Fass/Vome
Biome: Cave

Bait: Unneeded
Rarity: Common

Drops
Benign Infested Tumor (Small x3 , Medium x4 , Large x8 )
Ferment Bladder (Small x2 , Medium x3 , Large x6 )
Waxen Sebum Deposit (Small x3 , Medium x3 , Large x3 )

"These fish were purposefully contaminated with the infestation as an Entrati 'experiment'. They feed off the organic deposit in cave systems"

Catching info

Cycle: Fass
Biome: Cave

Cycle: Vome
Biome: Surface, Fass Residue hotspot

Bait: Processed Fass Residue
Rarity: Rare

Drops
Benign infested tumor (Basic x2, Medium x4, Large x8)
Biotic Filter (Basic x1, Medium x1, Large x1)
Pustulent Cognitive Nodule (Basic x1, Medium x1, Large x2)
Tubercular Gill System (Basic x1, Medium x2, Large x2)
Ferment Bladder (Basic x2, Medium x4, Large x6)

"As ravenous as the Infestation itself, this fish feeds on the remains of others. It shuns the light, preferring an enclosed cave environment."

Catching info

Cycle: Fass/Vome
Biome: Cave

Bait: Unneeded
Rarity: Common

Drops
Benign Infested Tumor (Small x3, Medium x4, Large x8)
Ferment Bladder (Small x3, Medium x4, Large x6)
Dendrite Blastoma (Small x1, Medium x1, Large x )

"A triumph of Orokin bio-engineering, these hardy fish have adapted to the Deimos environment and seem oddly resistant to Infestation. They thrive in cave environments."

Catching info

Cycle: Fass/Vome
Biome: Cave (hotspot)

Bait: Vome Residue recommended

Drops
Benign Infested Tumor (Basic x3, Adorned x4, Magnificent x8)
Tubercular Gill System (Basic x2, Adorned x3, Magnificent x5)
Spinal Core Section (Basic x2, Adorned x2, Magnificent x2)

"Formerly Orokin scavengers, these fish succumbed to the Infestation long ago and now greedily feast on floating spores. They are found all over the surface of Deimos."

Catching info

Cycle: Fass
Biome: Surface

Bait: Unneeded
Rarity: Common

Drops
Benign Infested Tumor (Small x2, Medium x4, Large x6)
Ferment Bladder (Small x2, Medium x3, Large x4)
Pustulent Cognitive Node (Small x1, Medium x1, Large x1)

"A living fossil hearkening back to the Orokin era, this elusive fish hides below the surface of Exocrine pools in the deepest caverns it can find. Unlike Infested fish breeds, it has no ability to hover."

Catching info

Cycle: Fass/Vome
Biome: Cave (hotspot)

Bait: Vome Residue recommended
Rarity: Uncommon

Drops
Benign Infested Tumor (Basic x2, Adorned x4, Magnificent x6)
Tubercular Gill System (Basic x2, Adorned x4, Magnificent x6)
Biotic Filter (Basic x2, Adorned x2, Magnificent x2)

"These hefty fish are cannibalistic. They rise by Vome's light to absorb rare gases, retreating when Fass ascends to devour their smaller kin in their lairs."

Catching info

Cycle: Vome
Biome: Surface

Bait: Fass Residue recommended
Rarity:

Drops
Benign Infested Tumor (Small x2, Medium x4, Large x6)
Ferment Bladder (Small x2, Medium x4, Large x6)
Sporulate Sac (Small x1, Medium x1, Large x1)

"The Infestation has suborned these fish to its own purposes, using them as antibodies to repel the non-Infested. They swim through and above the Exocrine found on Deimos' surface."

Catching info

Cycle: Fass/Vome
Biome: Surface

Bait: Unneeded
Rarity: Common

Drops
Benign Infested Tumor (Small x2, Medium x3, Large x6)
Ferment Bladder (Small x2, Medium x3, Large x6)
Saturated Muscle Mass (Small x1, Medium x1, Large x1)

"This exceptionally rare breed of fish is almost extinct, as its gilded Orokin flesh has a special savor for predators. It warily conceals itself in caves."

Catching info

Cycle: Fass
Biome: Cave (hotspot)

Bait: Processed Vome Residue recommended
Rarity: Rare

Drops
Benign Infested Tumor (Basic x2, Adorned x4, Magnificent x6)
Cranial Foremount (Basic x2, Adorned x2, Magnificent x2)
Tubercular Gill System (Basic x2, Adorned x4, Magnificent x10)

"Crammed with redundant, mutated internal organs, this pungent fish mingles Orokin and Infested ancestry. It is confined to the Exocrine and is only active by the light of the Wyrm Fass."

Catching info

Cycle: Fass
Biome: Surface (hotspot)

Bait: Fass Residue recommended
Rarity: Uncommon

Drops
Benign Infested Tumor (Basic x3, Adorned x4, Magnificent x6)
Tubercular Gill System (Basic x2, Adorned x3, Magnificent x4)
Ferment Bladder (Basic x2, Adorned x3, Magnificent x4)
Saturated Muscle Mass (Basic x1, Adorned x1, Magnificent x1)

"Whatever higher functions this fish once had have been consumed, leaving it a mere automaton of metal and flesh. If ekes out a primitive existence in cave systems."

Catching info

Cycle: Fass/Vome
Biome: Cave

Bait: Fass Residue recommended
Rarity: Uncommon

Drops
Benign Infested Tumor (Basic x3, Adorned x4, Magnificent x6)
Spinal Core Section (Basic x2, Adorned x2, Magnificent x2)
Dendrite Blastoma (Basic x1, Adorned x1, Magnificent x1)
Tubercular Gill System (Basic x2, Adorned x3, Magnificent x4)
Ferment Bladder (Basic x2, Adorned x3, Magnificent x4)

Thanks very much for using my guide.
I hope you found it useful for your fishing endeavours