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Groundfish Assessment Program

Caristius macropus
Figure 1. Photograph of Caristius macropus from southeastern Alaska. Photo by David Csepp.
 

Morphology of Bigmouth Manefish From the Eastern North Pacific Ocean

Research cruises by the Alaska Fisheries Science Center occasionally encounter rare fish species, and capture of these fish provides a unique opportunity to increase our knowledge of their morpholology, distribution, and habitat. Such an opportunity arose on 8 April 2003, when scientists from ABL caught a juvenile bigmouth manefish, Caristius macropus, (Fig. 1) in Lynn Canal, southeastern Alaska. The capture of this specimen initiated the complete morphological examination of all preserved specimens of C. macropus from Alaska in order to report detailed morphological and meristic information on these fish in Alaska. This was a joint project involving scientists from both ABL and the AFSC’s Resource Assessment and Conservation Engineering (RACE) Division. Data from this study provide additional information on the morphological variation and geographic distribution of this species and form a basis for comparison with specimens from other regions and with other species in the manefish family.

Caristiidae (manefish or veilfish) is a rare family of bathypelagic fishes characterized by an elongate fragile dorsal fin originating on the head and a fleshy sheath along the base of the dorsal and anal fins. Caristius macropus has been reported in the eastern North Pacific Ocean, but its distribution in Alaska waters and its general biology are poorly known. Before this southeastern Alaska collection, the only bigmouth manefish reported in Alaska waters were from infrequent collections in the eastern Aleutian Islands or farther north in the eastern Bering Sea (Fig. 2 below).
 

Map of Caristius macropus distribution, see caption
Figure 2.  Distribution of Caristius macropus in the eastern North Pacific Ocean including specimens examined for this study (circles), specimens captured in commercial midwater fishing operations and discarded (squares), and 200 m contour line.  Squares represent more than 25 records.
 

Most of the bigmouth manefish specimens examined in this study were collected by fishery observers in the AFSC’s North Pacific Groundfish Observer Program during midwater trawl fisheries between 1983 and 2003 that targeted walleye pollock. The specimen from southeastern Alaska in 2003 was also collected from a midwater trawl, but the trawl was deployed during a hydroacoustic survey by ABL scientists. Depths of previous reported captures ranged from 135 to 684 m.

A total of 14 specimens were examined for morphology and meristics. Results indicated that proportional measurements, as well as meristics, of the 14 specimens of C. macropus from Alaska were similar to those from other areas of the North Pacific Ocean. The specimens examined for this study do not significantly differ in any of these characteristics from the original species description in 1903, nor do they differ consistently from previously published records of this species from the North Pacific Ocean. Therefore, we consider all examined material from the subarctic North Pacific Ocean to belong to C. macropus.

The specimen collected in southeastern Alaska represents the first known record of this family from the Gulf of Alaska and from protected inside waters, as well as the smallest specimen examined and the first specimen collected from coastal waters. All specimens of C. macropus previously reported in the eastern North Pacific Ocean have been collected in the mesopelagic zone in unprotected open ocean waters. The collection of a C. macropus in protected inside waters of southeastern Alaska adds a new habitat for this species and gives C. macropus a wider distribution than previously described.

By David Csepp (ABL) and Duane Stevenson (RACE)
 

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