LARVAL DEVELOPMENT OF PACIFIC TOMCOD, MICROGADUS PROXIMUS, 



IN THE NORTHEAST PACIFIC OCEAN WITH COMPARATIVE NOTES ON 



LARVAE OF WALLEYE POLLOCK, THERAGRA CHALCOGRAMMA, AND 



PACIFIC COD, GADUS MACROCEPHALUS (GADIDAE) 



Ann C. Matarese, Sally L. Richardson, and Jean R. Dunn^ 



ABSTRACT 



A developmental series from yolk-sac larvae through juveniles (2.7-46.6 mm SL) of Microgadus 

 proximus from the northeast Pacific Ocean is described and illustrated. Larvae hatch at approximately 

 2.7 mm SL and the yolk is absorbed by 3.0 mm SL. Notochord flexion begins between 8.0 and 10.0 mm 

 SL, is completed at 15.0 mm SL, and transformation occurs between 22.0 and 28.0 mm SL. Larvae have 

 specific pigment patterns, particularly in the postanal region where melanophores are arranged in two 

 bars, anterior and posterior. At 5.0-6.0 mm SL, the anterior bar is located at 41-53% SL and the 

 posterior bar is at 61-74*^^ SL. Melanophore patterns on the head, gut, and caudal region also distin- 

 guish M. proximus. The occurrence of larvae taken within 18 km of shore off Oregon during plankton 

 surveys in 1971-72 is discusssed, and data indicate a winter-spring spawning period. 



A combination of pigmentation characters, primarily the length and position of the anterior and 

 posterior pigment bars, and meristic counts can distinguish larvae of M. proximus from Theragra 

 chalcogramma and Gadus macrocephalus . The anterior bar is located at 47-55% SL in T. chalco- 

 gramma and at 40-57% SL in G. macrocephalus. The posterior bar is located at 69-79% SL in T. 

 chalcogramma and at 59-81% SL in G. macrocephalus. Both T. chalcogramma and G. macrocephalus 

 have 4 rays on the superior hypural element while M. proximus has 5 rays. Other characters useful in 

 separating the three species include head, gut, mediolateral, postanal, and caudal pigment and stripe 

 continuitv. 



Problems have been encountered in distinguish- 

 ing larvae of Pacific tomcod, Microg'adusproximas 

 (Girard); walleye pollock, Theragra chalco- 

 gramma (Pallas); and Pacific cod, Gadus mac- 

 rocephalus (Tilesius), in samples from the north- 

 eastern Pacific Ocean where these three species 

 might cooccur (Waldron 1972; Dunn and Naplin^). 

 Larvae of T. chalcogramma were described by 

 Gorbunova (1954) and Yusa (1954). Larvae of G. 

 imorhua ) macrocephalus larvae were described by 

 Gorbunova (1954), Uchida et al. (1958), and 

 Mukhacheva and Zviagina (1960). In this report 

 we provide the first published description of the 

 larvae of M. proximus and comparative material 

 on larvae of T. chalcogramma and G. mac- 

 rocephalus that should enable workers to identify 



larvae of these three gadids in mixed samples. 

 Eggs and larvae of the Atlantic tomcod, Micro- 

 gadus tomcod, were described by Booth ( 1967), but 

 eggs of M. proximus are unknown. 



The geographic range of M. proximus extends 

 from off central California (Isaacson 1965) to the 

 Gulf of Alaska and Unalaska Island (Wilimovsky 

 1964). Their presence in the Bering Sea remains 

 unconfirmed , although they were reported to occur 

 in the Bering Sea by Tanner (1894) and Hart 

 ( 1973). Microgadus proximus was not captured in 

 the eastern Bering Sea during extensive multives- 

 sel groundfish surveys in 1974 (Pereyra et al. ) or 

 in 1976 (Bakkala and Smith ). Microgadus prox- 

 imus is found from near-surface waters to ap- 



^Northwest and Alaska Fisheries Center, National Marine 

 Fisheries Service, NOAA, 2725 Montlake Boulevard East, 

 Seattle, WA 98112. 



^Gulf Coast Research Laboratory, East Beach Drive, Ocean 

 Springs, MS 39564. 



^Dunn, J. R., and N. A. Naplin. 1974. Fish eggs and larvae 

 collected from waters adjacent to Kodiak Island, Alaska, during 

 April and May, 1972. Unpubl. manuscr.. 61 p. Northwest and 

 Alaska Fisheries Center, National Marine Fisheries Service, 

 NOAA, 2725 Montlake Blvd. E., Seattle, WA 98112. 



Manuscript accepted May 1980. 



FISHERY BULLETIN: VOL. 78, NO. 4, 198L 



■•Pereyra, W. T, J. E.Reeves, and R.G. Bakkala. 1976. De- 

 mersal fish and shellfish resources of the eastern Bering Sea in 

 the baseline year 1975. Unpubl. manuscr. Vol. 1, 619 p.; Vol. 

 2, 534 p. Northwest and Alaska Fisheries Center, National 

 Marine Fisheries Service, NOAA, 2725 Montlake Blvd. E., 

 Seattle, WA 98112. 



^Bakkala, R. G., and G. B. Smith. 1978. Demersal fish re- 

 sources of the eastern Bering Sea: Spring 1976. Unpubl. 

 manuscr, Vol. 1. 234 p.; Vol. 2. 404 p. Northwest and Alaska 

 Fisheries Center, National Marine Fisheries Service, NOAA, 

 2725 Montlake Blvd. E., Seattle, WA 98112. 



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