DEVELOPMENT OF LARVAL SMOOTH FLOUNDER, LIOPSETTA PUTNAMI, 

 WITH A REDESCRIPTION OF DEVELOPMENT OF WINTER FLOUNDER, 

 PSEUDOPLEURONECTES AMERICANUS (FAMILY PLEURONECTIDAE)' 



Wayne A. Laroche^ 



ABSTRACT 



Larval development is described lor the first time for Liopsetta putnami and redescribed for Pseudo- 

 pleuronectes amenca«!/s (Pleuronectidae). These species cooccur as larvae in Gulf of Maine estuaries 

 during the spring and have previously been difficult to separate, especially as small larvae, due to their 

 similar development and the lack of adequate published descriptions. Characters which distinguish L. 

 putnami from P. americanus larvae include: presence of darkly pigmented eyes in yolk-sac larvae; lack 

 of internal melanophores over the notochord in larvae greater than 3.2 mm; lack of melanophores on 

 the fins of yolk-sac, preflexion, and flexion larvae; and higher ratio of snout to anus length /standard 

 length (averages 43.6 and 41.2'7f standard length for yolk-sac and preflexion larvae versus 33.3 and 

 37.69f standard length for yolk-sac and preflexion larval P. americanus). 



The smooth flounder, Liopsetta putnami (Gill), 

 Family Pleuronectidae, occurs in the western 

 North Atlantic Ocean from Ungava Bay, Quebec, 

 to Providence, R.I. It is found chiefly over muddy 

 bottoms in estuaries and nearshore, marine 

 waters <10 m deep (Bigelow and Schroeder 1953; 

 Leim and Scott 1966). The winter flounder, 

 Pseudopleuronectes americanus (Walbaum), Fam- 

 ily Pleuronectidae, occurs from Battle Harbour 

 and Windy Tickle, Labrador (lat. 55°45' N), to 

 Georgia. It is caught over hard bottoms to depths of 

 =142 m on the offshore fishing banks and also in 

 estuaries and nearshore, marine waters (Bigelow 

 and Schroeder 1953; Leim and Scott 1966). From 

 Providence, R.I., northwards, L. putnami and P. 

 americanus cooccur in shallow coastal and es- 

 tuarine waters where both are known to spawn 

 (Bigelow and Schroeder 1953). 



Previously, two large larvae and one small 

 juvenile L. putnami have been illustrated and de- 

 scribed (Laszlo 1972), while larval and juvenile P. 

 americanus have been illustrated and their devel- 

 opment briefly described in various publications 

 (Sullivan 1915; Breder 1923; Bigelow and Welsh 

 1925; Bigelow and Schroeder 1953; Scotton et al. 

 1973; Lippson and Moran 1974; Klein-MacPhee 



'Contribution No. 139 from the Ira C. Darling Center, Univer- 

 sity of Maine. Walpole, Maine. Supported in part by a con- 

 tract from Maine Yankee Atomic Power Company to the Ira C. 

 Darling Center of the University of Maine, Orono. 



^Ira C. Darling Center, University of Maine, Walpole, Maine; 

 present address: Gulf Coast Research Laboratory, PO. Drawer 

 AG, Ocean Springs, MS 39564. 



1978; Martin and Drewry 1978; and others). How- 

 ever, existing descriptions of P americanus do not 

 accurately present all characters necessary for re- 

 liable separation of small larvae when the species 

 cooccur. 



This paper describes the larval development of 

 L. putnami for the first time from reared and 

 field-collected specimens, redescribes the larval 

 development o{ P. americanus , and compares the 

 two. 



METHODS 



Two ripe female and one ripe male L. putnami 

 were collected from the cooling water intake 

 screens of the Maine Yankee Atomic Power Plant 

 located on Montsweag Bay, Wiscasset, Maine, on 7 

 February 1974. Most L. putnami collected on that 

 date were spent. The ripe fish were artificially 

 spawned, and the eggs were fertilized in the field. 

 Eggs were kept at 5° C in darkened containers of 

 gently aerated 23%o salinity water, conditions ap- 

 proximating those at the capture site. Field- 

 collected larvae were captured in February and 

 March and also were reared in the laboratory. Lar- 

 vae were fed field-collected plankton. 



Larvae of both L. putnami and P. americanus 

 were collected and preserved in 3-5% Formalin^ 

 during 1972, 1973, and 1974 from the Sheepscot 



^Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



Manuscnpt accepted April 1980. 



FISHERY BULLETIN: VOL. 78. NO. 4, 1981. 



897 



