Abstract.- The sandi'lsh family 

 Trichodontidae is comprised of two 

 species endemic to the boreal Pacific: 

 Arctoscopus japonicus is a common 

 demersal fish of commercial impor- 

 tance in the western area around 

 northern Japan, while Trichodon tri- 

 chodon is found in the eastern waters, 

 from Alaska to California, although 

 there is no fishery for this species. 

 The two species share many similar 

 reproductive features such as large 

 demersal eggs of 3.3-3.5 mm diam- 

 eter, moderate fecundities of 1000- 

 2000 eggs, and peculiar spawning 

 habits on rocky shores. However, 

 there are striking contrasts in sev- 

 eral reproductive and early-life-his- 

 tory traits: the shape of the egg mass 

 is spherical in A. japonicus versus 

 an irregular shape in T. trichodon; 

 spawning substrate is mostly Sargas- 

 sum spp. versus rock; incubation 

 period is about 2 months versus near- 

 ly 1 year; and, at hatching, T. tricho- 

 don has precocious pectoral and 

 caudal rays as well as preopercular 

 spines. Despite these differences, lar- 

 vae of both species appear in the 

 spring season. These features are 

 discussed in relation to the contrast- 

 ing thermal regimes of the surface 

 waters characteristic of each species. 

 It is suggested that /I. japonicus has 

 a more derived reproductive style 

 than T. trichodon, including a typical 

 pattern of indirect ontogeny. The 

 remarkable seasonal thermal events 

 in Japanese coastal waters may be 

 responsible for the notable abun- 

 dance of ^. japonicus. 



Contrast \n Reproductive Style 

 Bet>A/een Two Species of Sandfislies 

 (Family Trichodontidae) 



Muneo Okiyama 



Ocean Research Institute. University of Tokyo, 

 Minamidai, Nakano, Tokyo 164, Japan 



15-1 



Manuscript accepted 13 March 1990. 

 Fishery Bulletin. U.S. 88:543-549. 



The family Trichodontidae is a small 

 family of marine fishes endemic to 

 the boreal Pacific comprised of two 

 species, Arctoscopiis japcmieus (Stein- 

 dachner) from the western Pacific 

 around Japan and Trichodon tricho- 

 don (Tilesius) from the eastern Pacif- 

 ic, ranging from Alaska to California. 

 As indicated by the common name 

 "sandfishes," they typically lie partly 

 buried in the bottom (Nelson 1984). 

 Due to peculiar morphological and 

 ecological features, they have been 

 placed at various times in different 

 groups of fishes such as the Percoi- 

 dei (Matsubara 1963) and Blennioidei 

 (Greenwood et al. 1966). 



The biology of A. japonicus has 

 been extensively studied because of 

 its special importance to commercial 

 fisheries in northern Japan and 

 Korea (for review, see Ochiai and 

 Tanaka 1986). For T. trichodon, how- 

 ever, information is only briefly docu- 

 mented in the literature (Fitch and 

 Lavenberg 1975, Eschmeyer and 

 Herald 1983), except for Marliave 

 (1981) and Bailey et al. (1983) who 

 reported the early life history in de- 

 tail, and Allen and Smith (1988) who 

 quantitatively illustrated aspects of 

 its zoogeography. 



These studies and our own ob- 

 servations, mostly in the northern 

 Sea of Japan, enable us to compare 

 life history traits of these fishes 

 and to discuss probable life strate- 

 gies associated with zoogeography. 

 The notable fluctuation of the stocks 

 of A. japonicus is also considered 

 from the standpoint of comparative 

 ecology. 



Comparison between 

 Arctoscopus Japonicus 

 and Trichodon trictiodon 



Distribution 



The family Trichodontidae is restricted 

 in distribution to the coastal boreal 

 regions of the North Pacific between 

 about 35°N and 60°N (Fig. 1). Al- 

 though Schmidt (1950) reported the 

 occurrences of A. japonicus from 

 Akutan Bay and the vicinity of Sitka 

 Island, in the Gulf of Alaska, these 

 records seem questionable (Esch- 

 meyer and Herald 1983). Perhaps 

 these two species have distinct geo- 

 graphica ranges, separated by longi- 

 tude 160-170°E. Arctoscopus japo- 

 nicus occurs over an extensive area 

 on the western side, including the off- 

 shore regions; it is extremely abun- 

 dant in the Sea of Japan and the 

 Pacific coast off Hokkaido, where 

 catches amounted to 3.8 x 10'* tons in 

 1968 (Ochiai and Tanaka 1986). Tri- 

 chodon trichodon is an eastern Pa- 

 cific form with a wider range from 

 Kamchatka to southeast of San Fran- 

 cisco, California; there is no fishery 

 for this species, but it is fairly com- 

 mon throughout the coastal waters 

 (Hart 1973, Fitch and Lavenberg 

 1975, Eschmeyer and Herald 1983, 

 Allen and Smith 1988). 



Depth range is variable from the 

 surface to about 400 meters in both 

 species; however, the main life zones 

 are slightly different for the two spe- 

 cies. Arctoscopus japonieus in the Sea 

 of Japan usually occurs at moderate 

 depths of 200-300 m, with optimum 



543 



