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Luring Behavior in the Scorpionfish, Iracundus Signifer

AbstractIn October, 1970, laboratory observations were conducted on fishes collected from the hull of a 12 meter boat which had remained on the ocean bottom in 70 meters of water for over five months. Included in the collection were three live specimens of the scorpionfish, Iracundus signifer Jordan and Evermann. These specimens displayed a type of luring behavior unlike any pattern described previously. Prior to feeding, the camouflaged scorpionfish raised its spinous dorsal fin and began snapping it from side to side in a characteristic fashion. Colors on the fin intensified during the display. The image of a small fish, complete with eye, mouth and dorsal fin, became visible on the fin. Prey fish, attracted within range, or at least distracted by the luring, were attacked by the scorpionfish and rapidly swallowed. The most comparative patterns in vertebrates are seen in the highly diversified angler-fishes, although members of the fresh water mussel family, Lampsilidae, display a similar lure in the attraction of host fishes for their larvae. The behavioral and morphological components of luring in I. signifer are seen individually among other members of the family Scorpaenidae, although none appear to have evolved a coordinated luring pattern closely similar to I. signifer. Experimental and observational data indicate that erection and movement of the lure may elicit a simple behavioral response, not directly related to the fishlike qualities of the lure. The evolution of this pattern is considered.

サケ・マス用魚探機の試作とその試験結果について

The writers have already published (1967) a study on the efficiency of the vertical fish finder used in the Northern Pacific salmon fishing grounds in regard to the sigle fish image constituted by a single fish image of Alaska pollack, but not by that of salmon and trout. So we carried out experiments for the purpose of developing a salmon fish finder. The performance of fish finder for salmon, having a frequency of 28 KHZ, is as follows: 1. The results of various experiments by the present writers as well as by others, prove that the swimming layer of salmon at daytime, and also at nighttime, is not more than 50m in depth. So the detection layer need not necessarily cover deeper than 50m in depth. 2. The reason why on salmon image appear with the use of the vertical fish finder may perhaps be due to the fact that the salmon run away as the fishing boats approach, thus slipping out of the sound beam of the fish finder. The direction of the sound beams of our new salmon fish finder, manufactured for trial purposes, can be transmitted towards the ship side downward at 30° oblique. 3. In order to separate the image of salmon from that of Alaska pollack, we attached a special circuit (fish discriminating circuit) to let the smaller reflection level of Alaska pollack cut off because of its smaller size compared with that of salmon, and also a logarithm amplifier to supplement a propagation attenuation of ultrasonic waves by distance. The results of such experiments proved a close correlation between the number of a single fish image as recorded by the net setting and the number of salmons caught by the gill net next morning. The recorded single image of fish is reasonably identified to be that of salmon.