(Anonymous 1976; Prescott and Moore 1976). 

 Silver hake, normally of variable abundance here 

 (Bigelow and Schroeder 1953) was also abundant 

 during 1976. On several different occasions, 

 groups of 6-30 white-sided dolphins were seen by 

 one of us (SKK) swimming close to pods of either 

 finback whale, Balaenoptera physalus, or 

 humpback whale, Megaptera novaeangliae , and 

 apparently feeding with them. 



Acknowledgment 



We are grateful to the crew of the MV Exxon Bay 

 State for procuring this specimen; to John E. Fitch, 

 California Department of Fish and Game, for 

 otolith identification; and to Fred Nichy, North- 

 east Fisheries Center, National Marine Fisheries 

 Service, NOAA, Woods Hole, Mass., for providing 

 data on otolith growth. 



Literature Cited 



ANONYMOUS. 



1976. Rise in squid Down East traced to warmer waters. 

 Ellsworth (Maine) American, August 26, 1976, p. 1. 

 BIGELOW, H. B., AND W. C. SCHROEDER. 



1953. Fishes of the Gulf of Maine. U.S. Fish Wildi. Serv., 

 Fish Bull. 53, 577 p. 

 NiCHY, F. 



1969. Growth patterns on otoliths from young silver hake, 

 Merluccius bilinearis (Mitch.). Int. Comm. Northwest 

 Atl. Fish. Res. Bull. 6:107-117. 

 PRESCOTT, R., AND M. MOORE. 



1976. Cape Cod squid influx and pelagic bird gathering. 

 Event 93-76, The Center for Short-Lived Phenomena, Re- 

 view of Annual Events. Camb., Mass., Nov. 19, 1976. 

 SCHEVILL, W. E. 



1957. Lagenorhynchus acutus o^ Cape CoA. J. Mammal. 

 37:128-129. 



Sergeant, D. E., and H. D. Fisher. 



1957. The smaller Cetacea of eastern Canadian waters. 

 J. Fish. Res. Board Can. 14:83-115. 



College of the Atlantic 

 Bar Harbor, ME 04609 



10 Riggs Street 

 Gloucester, MA 01930 



103 Riverdale Drive 

 Orono, ME 04473 



Steven K. Katona 



Salvatore a. Testa VERDE 



Bradley Barr 



reciprocal hybridization between 



the california and gulf of california 



grunions, leuresthes tenuis and 



leuresthes sardina (atherinidae) 



The California grunion, Leuresthes tenuis, and the 

 Gulf of California grunion, L. sardina, are the only 

 fishes that temporarily leave the water during 

 spring high tides to deposit their eggs in beach 

 sand (Walker 1952). The eggs develop in the 

 nearly dry sand and hatch when uncovered and 

 agitated by the surf of the next series of high tides. 



The grunions have an allopatric distribution. 

 The California grunion ranges from Monterey 

 Bay, Calif., to Bahia Magdalena, Baja California 

 Sur. The Gulf grunion is endemic to the Gulf of 

 California, ranging from Bahia Concepcion, Baja 

 California Sur, and Guaymas, Sonora, Mexico to 

 the mouth of the Rio Colorado (Moffatt and Thom- 

 son 1975). 



Recent comparisons show that morphological, 

 physiological, and behavioral differences exist be- 

 tween the grunions. Morphologically very similar, 

 the most diagnostic characterictics distinguishing 

 them are lateral scale row counts; the mean 

 number in L. tenuis is 75 and in L. sardina is 55. 

 Gulf grunion adults are also significantly longer, 

 more slender, have a smaller eye diameter, and 

 are more lightly pigmented than those of the 

 California grunion (Moffatt 1974; Moffatt and 

 Thomson 1975). Gulf of California grunion have 

 wider embryonic and larval thermal tolerances, a 

 higher larval preferred temperature, and wider 

 larval salinity tolerances (Reynolds and Thomson 

 1974a, b, c; Reynolds et al. 1976, 1977; Moffatt 

 1977). 



Light response remains positive in Gulf grunion 

 through adulthood, whereas the response shifts 

 from positive in the larvae to negative in the 

 adults of the California grunion (Walker 1952; 

 Reynolds and Thomson 1974c; Reynolds et al. 

 1977). In response to the shorter wave period in 

 the northern Gulf of California, the duration of the 

 spawning act of the Gulf grunion females is much 

 briefer than that of the California grunion females 

 (Thomson and Muench 1976; Muench 1977). 



Only recently has the congeneric status of the 

 grunions been recognized (Moffatt 1974; Moffatt 

 and Thomson 1975). Evidence to date indicates 

 that the California grunion, the less primitive of 

 the two species, has adapted to the less fluctuating 

 tidal and thermal regimes of the California coast, 

 following isolation from an ancestral type by the 



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