SHORTPAPERS 347 Kemp, S. 1910. The Decapoda Natantia of the Coasts of Ireland. Sci. Invest. Fish. Br. Ire. 1908(1): 1-190, pIs. 1-23. Lo Bianco, S. 1903. Le peche abissali esequite da F. A. Krupp col Yacht Puritan nelle adiacenze di Capri ed in a1tre localita del Mediterraneo. Mitt. Zoot. Sta. Neapet. 16: 109-279, pIs. 7-9. MacPherson, E. 1978. On the occurrence of Richardifla fredericii Lo Bianco, 1903 (Decapoda; Stenopodidae) in Spanish waters. Crustaceana 35(1): 107-109. Milne Edwards, A. ]881. Compte rendu sommaire d'une exploration zoologique faite dans I'Atlantique a bord du navire Ie Travailleur. C. R. Acad. Sci. Paris 43: 931-940. Zariquiey Alvarez, R. 1968. Crustaceos Decapodes Ibericos. Instit. Invest. Pesq. Barcelona 32: 1- 510. DATE ACCEPTED: April 9, 1981. ADDRESS: Duke Ufliversity Marifle Laboratory, Beaufort, North Carolifla 285/6 U.S.A. BULLETINOFMARINESCIENCE.32(1): 347-350. 1982 SEASONAL SPAWNING CYCLES OF TWO CALIFORNIA FLATFISHES, PLEURONICHTHYS VERT/CALIS (PLEURONECTIDAE) AND HIPPOGLOSSINA STOMATA (BOTHIDAE) Stephen R. Goldberg The hornyhead turbot, Pleuronichthys verticalis and the bigmouth sole, Hip·- poglossina stomata are two of the common flatfishes that occur sympatrically in the coastal waters of southern California. P. verticalis is found from Magdalena Bay, Baja California and the northern Gulf of California to Point Reyes between depths of 9-187 m and H. stomata ranges from the Gulf of California to Monterey Bay between depths of 12-137 m (Miller and Lea, 1976). Budd (1940) and Fitch (1963) previously reported on spawning in P. verticalis. Eggs of both species are described in Sumida et al. (l979). This report contains the first information on the seasonal spawning cycle of H. stomata. MA TERIALS AND METHODS Fishes were collected off the coast of southern California by otter trawl at depths of 45-64 rn. Collections were taken from San Clemente (33°20'N, 117°38'W) to Santa Monica Bay (33°53'N, lI8°37'W). Specimens were analyzed from collections made from September 1974-0ctober 1979. Only female specimens were examined. Both species are medium sized flatfishes with P. verticaUs from my study averaging 198 mm standard length (SL) (range 142-250 mm) and H. stomata averaging 215 mm SL (range 150-283 mm). Fishes were preserved in 10% formalin. Histological sections from 140 P. vertica/is and 110 H. stomata ovaries were cut at 8 f..I.mand stained with Heidenhain iron hematoxylin (Humason, 1979). Seasonal gonosomatic indices (GSI) (ovary wt/fish wt x 100) were calculated from preserved ovaries. RESULTS Ovaries were histologically classified into four stages (Table 1). Stage 1 (re- gressed or regressing ovary): the non-spawning condition consists principally of primary oocytes (100 tLm diameter). Stage 2 (pre-vitellogenic): slightly enlarged vacuolated oocytes (230 tLm diameter) predominate prior to onset of yolk depo- sition. Stage 3 (vitellogenic): yolk deposition in progress. Stage 4 (spawning): mature (ripe) oocytes predominate. 348 BULLETIN OF MARINE SCIENCE, VOL. 32, NO. I, 1982 Table (, Monthly distribution of ovarian stages in the yearly spawning cycles of Hippoglossina stomata (Hs) and Pleuronichthys vertica/is (Pv) Percent Regressed or N Regressing Pre.vitellogenic Viteliogerue Spawning Month (Hs) (Pv) (Hs) (Pv) (Hs) (Pv) (Hs) (Pv) (Hs) (Pv) January 16 26 100 0 0 0 0 0 0 100 February 6 0 0 0 100 March 7 8 100 0 0 0 0 0 0 100 April 9 24 100 0 0 4 0 0 0 96 May 9 9 33 0 44 0 11 0 II 100 June 11 6 18 0 9 0 9 0 64 100 July 24 21 0 5 8 0 0 0 92 95 August I 3 0 0 0 0 0 0 100 100 September 9 7 22 14 0 0 0 0 78 86 October 18 25 28 16 0 8 0 0 72 76 December 6 5 100 0 0 0 0 0 0 100 H, stomata is a summer-fall spawner. Ovaries were regressed during winter (Table 1) and contained primary oocytes. GSI values were minimal (Fig. 1). Ovarian activity began in spring and was histologically evident with the appear- ance of pre-vitellogenic oocytes. The first female that was in spawning condition (Table 1) was collected in May. Spawning females predominated into October. GSI values were maximum during this time (Fig. 1). All December females were regressed indicating the spawning cycle concludes in autumn. As the smallest spawning female measured 162 mm SL, this is apparently the size that sexual maturity is first attained. The largest H. stomata female measured 283 mm SL. In contrast to the summer-fall spawning season of H. stomata, P. verticalis spawning appears to be a continuous year-round process (Table 1). Monthly gonosomatic indices did not significantly vary (Fig. 2) and the majority of females (at all times >75%) were in spawning condition throughout the year. It was only September-October when regressed females were common (Table 1) and even during these months most females were in spawning condition. The smallest spawning female measured 142 mm SL (minimum size required for sexual ma- turity); the largest 250 mm SL. Ovaries of spawning females of both species (Stage 4) contained a mode of mature eggs (>400 J.Lm) representing an imminent spawning. Some of these were hydrated. Hydration occurs just prior to spawning when mature eggs swell with fluid, become opaque and enlarge to approximately 600 J.Lm. Sumida et al. (1979) reported H. stomata eggs from plankton collections ranged from 1.22-1.38 mm diameter while P. verticalis eggs ranged from 1.00-1.16 mm. Also present in the ovaries of spawning females is a mode of vitellogenic eggs from a subsequent spawning as well as a vacuolated non-vitellogenic mode which will presumably mature later in the season. Postovulatory follicles (transitory remnants of the follicle wall from a recent spawning) were also noted in 15% of spawning H. stomata and 2.6% of spawning P. verticalis. DISCUSSION The considerably higher frequency of postovulatory follicles in H. stomata may possibly indicate spawning occurs more frequently than in P. verticalis. SHORT PAPERS 349 10,0 0 24 II ~ 10.0 26 0 2\ ;. 8,0 S 18 ~ I- B.O >- 0 ;: 25 06,0 >- <D 0 g 6.0 f-"- "- ~.,~,.~ ~ f- >- 4,0 ;: Q: ~ >- 4.0 <l a: > ~ ~ ~ 0 '~ ~.::! 0 .~n 2,0 .~J 2,0 I JAN MAR APR MAY JUN JUl AUG SEP OCT DEC JAN FEB MAR APR MAY JUN JUL AUG SEP OCT DEC Figure I. Seasonal gonosomatic indices for Hippoglossina stomata. Vertical line = range; horizon- tal line = mean; rectangle = 95% confidence interval. Sample size above each month. Figure 2. Seasonal gonosomatic indices for Pleuronichthys vertica/is. See Figure I for explanation of symbols. Thus, despite the longer spawning season of P. verticalis, the overall reproductive potential may not be higher. Postovulatory follicles were similar in morphology to those reported in other teleosts (Hunter and Goldberg, ]980). My observation of follicles in various stages of yolk deposition throughout the spawning period in H. stomata and P. verticalis suggests that successive batches of eggs are matured and spawned. This is indicative of a spawning cycle that differs fundamentally from that in which a single mode of eggs matures and is spawned, as occurs in the California flatfishes, Platichthys stellatus as described by Orcutt (1950) and Microstomus pacific us as described by Hagerman (1952). It is believed that both these species spawn only once a year. The spawning cycles of P. verticalis and H. stomata in southern California illustrate two contrasting reproductive patterns. H. stomata has a seasonal spawning cycle typical of fishes living in temperate waters, with females becoming reproductively active in late spring and remaining in this state into autumn. In contrast, P. verticalis spawning occurs throughout the year. Fitch (1963) similarly found females with ripe gonads throughout the year. This prolonged spawning period is similar to the type found in tropical and subtropical fishes (Nikolsky, 1963). It was reported in two marine cottids from southern California (Chitonotus pugetensis and Icelinus quadriceriatus) by Goldberg (1980). Frey (197]) similarly reported that Glyptocephalus zachirus (Pleuronectidae) were in spawning con- dition throughout the year. It was found by Budd (1940) that spawning in P. verticalis from Monterey Bay, California extends only from March to August suggesting this species may have a shorter reproductive period at higher latitudes. In contrast, most of the other flatfishes from the Pacific coast of North America appear to be seasonal breeders which spawn mainly during winter. Fitch and Lavenberg (1971) reported the following spawning periods for California flatfish- es: Platichthys stellatus (November-February); Microstomus pacificus (Nov em.. ber-March); Citharichthys sordidus (July-September); Paralichthys californicus (February-July). Frey (1971) reported: Parophrys vetulus (October-May); Eop" setta jordani (October-March). Hart (1973) gave several spawning reports for flatfishes from the Pacific coast of Canada and northwestern United States: Citharichthys sordidus (February); Hippoglossoides elassodon (March-late April); Isopsetta isolepis (February-late 350 BULLETIN OF MARINE SCIENCE. VOL. 32, NO.1. 1982 April); Lepidopsetta bilineata (February-April); Lyopsetta exilis (February- April); Psettichthys melanostictus (January-July); Platichthys stellatus (Febru- ary-April); Parophrys vetulus (January-March); Hippoglossus stenolepis (No- vember-January). Because H. stomata is a summer-autumn spawner, it differs from most of the above (with exception of C. sordidus) which are primarily winter spawners. The occurrence of spawning females throughout the year in P. verticalis is different from that which occurs in the great majority of western North American flatfishes. The advantages of this type of cycle are not clear at this time and further studies on the biology of this species will be necessary. ACKNOWLEDGMENTS I am grateful to M.