Midnight Mystery and Other Strange Fishes from the Deep

Sport Fishing readers try to stump the Fish Facts experts with strange catches.

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Q: I was out shibi (night) fishing and caught this fish that was swimming with the tombo (albacore) school. I was wondering if you know what kind of fish it is. Mahalo! Clinton Hinchcliff Kailua-Kona, Hawaii ******A**: What you have there is an escolar, Lepidocybium flavobrunneum. A member of the snake mackerel family (Gempylidae), these can be encountered by anglers fishing offshore in deep waters throughout tropical and temperate seas worldwide. Other close relatives in the same family include gemfish, hairtails and —the oilfish (Ruvettus pretiosus). The latter is superficially similar in appearance to the escolar but lacks the escolar's tunalike lateral keels on each side just ahead of the tail; it also has only one finlet behind the second dorsal and anal fins. Escolar are frequently bycatch in tuna longline fisheries and often marketed as white tuna. They are usually taken at depths of more than 600 feet off the continental shelf, particularly where such deep water is adjacent to coral atolls. However, escolar migrate upward at night, and roam into shallower waters as they follow diurnally migrating prey such as squid, crustaceans and smaller fish. Escolar can grow to substantial sizes, with the IGFA all-tackle record at 173 pounds, 12 ounces (from Cayman Islands in 2011). They’re reported to be very tasty, but the flesh is very oily (14 to 25 percent oil), and nearly all of this consists of a type of wax ester, which can have a significant laxative effect for some people. Humans lack the enzymes necessary to break the large wax-ester molecules into smaller, absorbable components, so they pass right on through — with decidedly purgative consequences for some who partake in excess (which can be as little as 5 ounces of fillet in a single sitting). Also, like other Gempylids (and tunas and mackerels), if not refrigerated very soon after capture, escolar can cause scombroid poisoning (debilitating but seldom deadly), from increased histamine levels in the fish’s flesh, a byproduct of bacterial decomposition. — **Ben Diggles **
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****A**:**** **While this is clearly a rockfish of the genus Sebastes, all of us rockfish-heads are puzzled as to exactly what species it might be. Four general possibilities present themselves. First, this fish might represent an undescribed (“new”) species. While this is possible, given the substantial amount of fish-survey work conducted by various groups in Alaskan waters, this seems like the least-likely prospect. Second, this could be an individual of a species normally found in another location, for instance off Russia or Japan. I guarantee it is not a species found south of Alaska. Unfortunately, after looking at images of all 30-plus western Pacific species of rockfishes, I can’t come up with any that look much like this one. Third, this fish might be a hybrid. Hybrids among rockfishes do occur but only pretty rarely. Only a genetic analysis would definitively prove if this were a hybrid. Thus, we come to what might be the most likely scenario — that this is an aberrant individual of a known species. The body shape is similar to two very abundant Alaskan species, the dark rockfish, Sebastes ciliatus, and the dusky rockfish, S. variabilis, although the color is somewhat off, and neither species has the black spotting we see here. At least one of my colleagues has, on occasion, seen dark rockfish with this body coloration. A number of rockfishes develop a type of skin cancer that creates black skin patches like those on this fish. However, all of this is just sophisticated hand waving. We can really identify this fish only if someone can save us one for examination. — Milton Love
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Q: I have noticed that once out of the water, bluefish expire very quickly; however, tautog and certain other bottom dwellers such as black sea bass or dogfish will live for hours out of the water. I’ve had tautog live on ice for well over three hours; they seemed to be breathing oxygen even when on the fillet table. Have certain species of fish adapted to the point that they have a hybrid lung/gill anatomy allowing them to live out of the water for extended periods of time? Brett Stone Miramar, Florida Click "next" to see the fish.
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A: While a number of variables can affect how long a fish survives out of water, one of the most important is a species' metabolic rate and corresponding oxygen demands. A very active species such as a bluefish has a considerably higher metabolic rate than a less-active species like a tautog, and thus requires more oxygen to produce the energy-supplying compounds it needs to stay alive. Normally, more-active fishes have larger, proportional gill-surface areas. When a fish is taken out of the water, its gill filaments usually collapse against each other, reducing the surface area available for gas exchange. Additionally, as the fish's gills dry out, oxygen absorption is further reduced since oxygen must first dissolve in a fluid before moving across a semipermeable membrane such as the surface of the gill filaments. Together, these factors help determine how long a fish survives out of water. Cooling a fish reduces its metabolic rate, so as long as a fish isn't cooled to the level where its enzyme systems stop functioning correctly, a cool fish will likely survive longer than one held at a warmer temperature. One other factor also comes into play: If a fish is unable to achieve sufficient gas exchange, carbon dioxide builds up in its tissues and is converted to carbonic acid. This causes a shift in the fish's pH, which can prove fatal. In fact, it has been suggested that fish deprived of gas exchange don't die from suffocation as much as from acidosis. — Ray Waldner
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