560 



Fishery Bulletin 98(3) 



tcn3t3«*'^ 



Figure 14 



Supporting elements of the pores of the supraorbital 

 canal of Lepidopsetta bilineata. UW 025197, 77.3 mm, 

 Puget Sound, WA. View of dorsal (right lateral* side. 

 Scale bar equals 5 mm. 



Psettichthys melarjostictus, and Inopsetta ischyra (a possi- 

 ble hybrid of Platichthys stellatus and Parophrys vetulus) 

 have a single pore. In Hippoglossoides elassodon and H. 

 robustus, a series of pores is found at the anterior exten- 

 sion of the supratemporal line, as depicted by Lindberg 

 and Fedorov (1993) for H. elassodon (their Fig. 33). These 

 pores are apparently part of the anterior extension of the 

 trunk lateral line, but ventrally the pores extend near the 

 dorsal orbital rim. In one specimen of H. elassodon exam- 

 ined lUW 040271), the pores extended nearly the same 

 length along the rim of the dorsal orbit as the length for 

 the same pores in some L. bilineata. 



Pleuronectid larvae are difficult to diagnose on the basis 

 of a simple set of characters. Pleuronectids are oviparous 

 and spawn planktonic or demersal eggs (about 0.66-4.5 

 mm), with homogenous yolk that is either pigmented or 

 not, and usually contains no oil. Among eastern North 

 Pacific pleuronectids, Lepidopsetta is the only genus that 

 produces demersal eggs, which are off-round and have a 

 sticky chorion that causes them to adhere to each other 

 or to a substrate (Pertseva-Ostroumova, 1961; Penttila, 

 1995). Pleuronectid larvae hatch between 1.7 and 16.0 

 mm; yolksac and preflexion larvae are slender, becoming 

 deeper-bodied during the postflexion stage. Larvae of Lepi- 

 dopsetta hatch at <3.0-4.5 mm; preflexion larvae are slen- 

 der and have moderate-size finfolds. 



Larval pigmentation (including finfold) varies consider- 

 ably in pleuronectids. A combination of pigment pattern 

 ( postanal bands, bars, and finfold i, meristic characters, and 

 size at development is needed for identification (Matarese 

 et al., 1989; Charter and Moser, 1996). Larvae with spe- 

 cial characters (e.g. Atheresthes larvae with head spines) 

 or high myomere counts (e.g. Embassichthys) are easily 

 distinguished. Other pleuronectid larvae are usually dis- 

 tinguished by a combination of pigmentation characters 



including the number of postanal bands and bars and fin- 

 fold pattern (Table 12). 



No single early life history character distinguishes larvae 

 of Lepidopsetta from other pleuronectid genera. Depending 

 on developmental stage, larvae of Lepidopsetta generally 

 are categorized by the presence of at least one postanal 

 bar (Table 12). Larvae of L. bilineata have a postanal pig- 

 ment pattern with four dorsal pigment patches (the poste- 

 riormost aligning with a ventral patch forming a caudal 

 bar), larvae of L. mochigarei have three dorsal patches 

 (the posteriormost aligns with a ventral pigment patch 

 approximating a caudal bar), whereas larvae of L.polyxys- 

 tra n. sp. have two dorsal pigment patches (the posterior- 

 most aligns with a ventral pigment patch forming a bar 

 located at about 2/3 of body length). Among other pleuro- 

 nectid genera that have a postanal band and bar pattern, 

 preflexion and early flexion larvae of Lepidopsetta may be 

 distinguished by the presence of a series of postanal ven- 

 tral midline melanophores and fewer pigment spots along 

 the notochord tip (Table 12). 



In general, lai-vae of L. bilineata closely resemble those 

 of Psettichthys among other genera (Table 12). Both have 

 alternating patches of pigment on dorsal and ventral 

 body margins, although Psettichthys has a series of small 

 patches on the dorsal and ventral finfold margins whereas 

 L. bilineata has isolated patches along the finfolds. A series 

 of postanal ventral melanophores is present in L. bilineata 

 and absent in Psettichthys. in which postanal pigment is 

 usually restricted to three or four large spots. Larvae of 

 L. bilineata generally have much less pigment on the jaws 

 and isthmus than do larvae of Psettichtys. 



Size at stage of development varies among species ( Table 

 13). Larvae of L. bilineata begin transformation at smaller 

 lengths than larvae of L. poly.xystra n. sp. or L. mochiga- 

 rei. Larvae of L. bilineata also have a larger orbit, shorter 

 snout-to-anus length, and a slenderer body (see Table 2 1. 



The juvenile stages of most eastern North Pacific pleu- 

 ronectids are poorly known. Traditional early life history 

 descriptions tvpically describe developmental stages on 

 the basis of eggs and larvae captured in plankton nets and 

 usually do not include transitional larvae that undergo 

 changes associated with a benthic existence. Plankton sur- 

 veys routinely use nets that do not effectively sample 

 bottom waters where many pleuronectid juveniles eventu- 

 ally settle. 



Pleuronectid juveniles can be separated by several char- 

 acters. Perhaps the most important character is the size at 

 which transformation occurs, although data are scarce on 

 when transformation is completed. Among taxa for which 

 data are available, eastern North Pacific pleuronectids can 

 be grouped into three categories based on approximate 

 transformation sizes: <15 mm SL, 15-30 mm SL, and >30 

 mm SL. Genera with at least one species transforming at 

 sizes <15 mm SL include Limanda, Platichthys. Pleuro- 

 nectes, and Pleuronichthys (sensu Cooper and Chapleau, 

 1998). Genera with larvae that transform at much larger 

 sizes (>30 mm SL) include Atheresthes. Embassichthys. 

 Glyptocephalus. Hippoglossoides. Micr-o.'itonuis. and Rein- 

 hardtius. Larvae of Lepidopsetta generally undergo trans- 

 formation between 15 and 25 mm SL. Other eastern North 



