Valle et aL: Habitat use by Paralichthys californicus and Paralabrax nebulifer 



647 



these relationships within bays is particularly im- 

 portant owing to the destruction and severe alter- 

 ation of about 75% of coastal estuary and wetland 

 habitats in southern California since 1900 (Califor- 

 nia Coastal Zone Conservation Commissions, 1975). 

 Reduced catches of California halibut, Paralichthys 

 californicus. may be due to the alteration or loss of 

 this nursery habitat within bays and estuaries, or to 

 both (Plummer et al., 1983; Kramer and Sunada, 

 1992; Kramer and Hunter^). 



California halibut is an important commercial and 

 sport fish in southern and central California. Barred 

 sand bass, Paralabrax nebulifer, is also an impor- 

 tant sport fish in southern California and ranks an- 

 nually among the top three species caught aboard 

 commercial passenger fishing vessels (Love et al., 

 1996a). Both of these fishes spawn in nearshore wa- 

 ters (Frey, 1971; Ono, 1992) and occupy embayments 

 during their early life history; newly settled and 

 larger juvenile California halibut are frequently 

 found over shallow, sandy substrata (Haaker, 1975; 

 Allen, 1988; Allen and Herbinson, 1990, 1991; 

 Kramer, 1990, 1991a, 1991b), whereas juvenile 

 barred sand bass are found in eelgrass beds (Feder 

 et al., 1974; Rosales-Casian, 1997). However, little 

 additional information is available on habitat use by 

 these and other fishes within these areas. 



Therefore, the purpose of our study was to deter- 

 mine 1) if abundances of juvenile California halibut, 

 barred sand bass, and other fishes differed between 

 eelgrass and unvegetated habitats, 2 ) whether these 

 abundances differed among sites within the bay, and 

 3) whether these differences were related to physi- 

 cal characteristics of eelgrass or abiotic factors. We 

 examined habitat use by collecting fishes with a beam 

 trawl towed in shallow eelgrass beds and nearby 

 unvegetated areas at three sites within a single bay. A 

 beam trawl was used because it collects smaller hali- 

 but and other flatfishes more effectively than beach 

 seines and otter trawls (Gunderson and Ellis, 1986; 

 Kramer, 1990; Kuipers et al., 1992) and allows com- 

 parison with other studies where similar gear was used. 



Materials and methods 



Study area and sampling 



Our study was conducted in Alamitos Bay (lat. 

 33°45'N, long. 118 = 07'W), which is a small embay- 



ment located at the southeastern boundary of Los 

 Angeles County in southern California. Alamitos Bay 

 was once an estuary of tidal marshes and mud flats. 

 It has been considerably modified by dredging, fill- 

 ing, and construction of homes, marinas, and two 

 jetties that mark the entrance. The bay is exposed to 

 semidiurnal tides with a mean range of 1. 1 m. Water 

 circulation is further enhanced by large amounts of 

 water drawn by two power stations that flush the 

 bay every 19 hours (Phillips^). Regardless of tidal 

 flux, there is a consistent flow of water into the bay 

 (Brown and CaldwelP). 



Sampling was conducted at three sites (Bay En- 

 trance, Belmont Shore, and Marine Stadium) sepa- 

 rated by at least one km (Fig. 1). At each site, sam- 

 pling occurred in two habitats, eelgrass (Zostera 

 marina) beds and nearby unvegetated sandy-mud 

 areas located about 40 m away. A weighted 1.6-m 

 beam trawl, equipped with skis, tickler chain, and 

 3.0-mm stretched-mesh netting, was towed parallel 

 to shore by two people on foot at low tide during the 

 lowest tides of the month. Tows were made during 

 daylight hours at depths from 0.3 m to 1.1 m, lasted 

 90 seconds, and covered approximately 56 m-. We 

 completed 2-5 tows, depending on tide height, in each 

 habitat at each site over four consecutive days. Sam- 

 pling was conducted monthly from May 1992 through 

 April 1993 (excluding February) and from Novem- 

 ber 1993 through December 1994. Bimonthly sam- 

 pling occurred from January 1995 through Novem- 

 ber 1995. All fishes were sorted, identified, counted, 

 and returned to the water. Most fishes were mea- 

 sured to the nearest mm standard length (SL) from 

 May 1992 through October 1994, whereas Califor- 

 nia halibut and barred sand bass were measured 

 throughout the study. Although California halibut 

 and barred sand bass undergo transformation at 

 about 7-9 mm SL and 11 mm SL, respectively (But- 

 ler et al., 1982; Ahlstrom et al., 1984; Gadomski et 

 al., 1990), all individuals <20 mm SL were consid- 

 ered to be "newly settled" or "newly recruited" (Allen 

 and Herbinson, 1990; Kramer, 1990; Love et al., 

 1996b). Larval and postlarval gobies (Brothers, 1975) 

 that were not identified further were classified as 

 "goby larvae." Other fishes not sexually mature based 

 on size at first maturity information were considered 

 to be juveniles. Water temperature, dissolved oxy- 

 gen, and salinity data were collected for most tows, 



' Kramer, S. H., and J. R. Hunter. 1987. Southern California 

 wetlandyshallow water habitat investigation. Southwest Fish- 

 eries Science Center, National Marine Fisheries Service, NOAA, 

 P.O. Box 271, La Jolla, CA 92038. Ann. Rep. for Fiscal Year 

 1987, 12 p. 



^ Phillips. K.W. 1978. A water and sediment study of Alamitos 

 Bay correlated with peak and minimal recreational aquatic ac- 

 tivities. City of Long Beach Chemical and Physical Testing 

 Laboratory, Long Beach, California. Unpubl. data. 



■^ Brown and Caldwell Environmental Sciences Division. 1979. 

 Embaynient ecology studies: physical oceanographic and water 

 quality data report. Southern California Edison, Unpubl. data. 



