EGGS AND LARVAE OF BUTTER SOLE, ISOPSETTA ISOLEPIS 

 (PLEURONECTIDAE), OFF OREGON AND WASHINGTON 



Sally L. Richardson/ Jean R. Dunn,^ and Nancy Anne Naplin^ 



ABSTRACT 



Development of butter sole, Isopsetta isolepis, is described from egg through benthic juvenile, based on 

 reared and field-collected specimens. 



Isopsetta isolepis eggs are planktonic, spherical, and transparent w^ith a narrow perivitelline space, 

 homogeneous yolk, and no oil globule. Diameters of 80 reared eggs averaged 0.93 mm (range 0.90-0.99 

 mm). Using light microscopy, early and middle stage eggs are indistinguishable from those of three 

 other pleuronectids, English sole, Parophrys vetulus, sand sole, Psettichthys melanostictus , and starry 

 flounder, Platichthys stellatus, with which they cooccur. Pigment patterns distinguish late stage /. 

 isolepis eggs from those o{ Psettichthys melanostictus and Platichthys stellatus. Because the late stages 

 of/, isolepis embryos vary widely in degree and character of pigmentation, they often cannot be reliably 

 separated from those of Parophrys vetulus. 



Larvae are readily distinguished by three bands of melanistic pigment on the tail region of the body 

 combined with myomere counts (39-42). Transformation from larva to juvenile takes place at about 

 18-23 mm. Larvae are abundant in nearshore coastal waters off Oregon and Washington in winter and 

 spring, where they cooccur with larvae of P. vetulus. Recently transformed benthic juveniles of/. 

 isolepis usually are found offshore rather than in the bay and nearshore habitats occupied by young 

 juvenile P. vetulus. 



This paper presents the first complete description 

 of development of the butter sole, Isopsetta isolepis 

 (Lockington), from egg through benthic juvenile. 

 Larvae of this species are common in the ichthyo- 

 plankton off Oregon and Washington where they 

 ranked fifth in overall abundance in April and 

 May 1967 (Waldron 1972) and third in a coastal 

 assemblage of larval fishes off Oregon in 1971-72 

 (Richardson and Pearcy 1977; Richardson'*). 



Isopsetta, a monotypic genus of the family 

 Pleuronectidae, ranges from Ventura, Calif., to 

 the Bering Sea (Miller and Lea 1972). It is usually 

 found in coastal waters although it has been re- 

 ported from the 274-366 m depth zone in western 

 Alaska (Demory 1971; Miller and Lea 1972; Hart 

 1973). Adult butter sole ranked 11th and 7th in 



'School of Oceanography, Oregon State University, Corvallis, 

 Greg.; present address: Gulf Coast Research Laboratory, Ocean 

 Springs, MS 39564. 



^Northwest and Alaska Fisheries Center, National Marine 

 Fisheries Service, NOAA, 2725 Montlake Boulevard East, Seat- 

 tle, WA 98112. 



^Northeast Fisheries Center Sandy Hook Laboratory, Na- 

 tional Marine Fisheries Service, NOAA, Highlands, NJ 07732. 



■•Richardson, S. L. 1977. Larval fishes in ocean waters off 

 Yaquina Bay, Oregon: abundance, distribution, and seasonal- 

 ity, January 1971 to August 1972. Oreg. State Univ., Sea 

 Grant Coll. Prog., Publ. ORESU-T-77-003, 73 p. 



biomass of all flatfishes taken during trawl sur- 

 veys off Oregon in 1971-72 and 1973-74 (Demory 

 et al.^) and 6th in biomass of all flatfishes off 

 Washington in both 1975 and 1976 (Barss et al.^). 

 Because it is a relatively small, <55 cm TL (total 

 length), slender fish (Miller and Lea 1972; Hart 

 1973), it is currently of only minor commercial 

 importance. 



Levings ( 1968) briefly described I. isolepis eggs 

 as single, nonadhesive, transparent, spherical, 

 without an oil globule, with a mean egg diameter 

 of 1.013 mm, although he did not illustrate them. 

 The eggs sank at salinities ss26.61%o but floated at 

 salinities &28.03%o. Levings concluded that the 

 eggs were demersal within Skidegate Inlet, 

 British Columbia, where bottom salinities were 

 24.96%o. Isopsetta isolepis larvae 4.8, 7.9, 10.0, and 

 15.5 mm long from Puget Sound were sketched by 

 Blackburn (1973) but were labeled Lyopsetta 

 exilis. He also provided short descriptions. 



Manuscript accepted December 1979. 

 FISHERY BULLETIN: VOL. 78, NO 2, 1980. 



^Demory, R. L., M. J. Hosie, N. TenEyck, B. O. 

 Forsberg. 1976. Marine resource surveys on the continental 

 shelf off Oregon, 1971-74. Oreg. Dep. Fish Wildl., Completion 

 Rep., June 1976, 49 p. 



«Barss, W. H., R. L. Demoiy, N. TenEyck. 1977. Marine 

 resource surveys on the continental shelf and upper slope off 

 Washington, 1975-76. Oreg. Dep. Fish Wildl., Completion 

 Rep., September 1977, 34 p. 



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