FISHERY BULLETIN: VOL. 81. NO. 3 



of amphipod crustaceans and polychaete worms 

 (Barnard 1970). In fact, the most abundant crusta- 

 cean, Ampelisca agassizi (A. compressa in Barnard 

 1970), is closely related to A. macrocephala, a major 

 prey of gray whales in the Bering Sea (Rice and Wol- 

 man 1971). The total abundance of infaunal inver- 

 tebrates in Laguna San Quintin is as high as 66,700 

 individuals/m 2 of bottom (Barnard 1970). Although 

 there are no benthic biomass data from San Quintin, 

 the species composition and abundance patterns 

 suggest a significant quantity of potential gray whale 

 prey. San Quintin may have been an important gray 

 whale habitat in the past, and in the last several years 

 has been visited by a few gray whales each season 

 (Sprague et al. 1978). 



The recent behavioral observations in the breeding 

 lagoons and the quantity of potential prey in Laguna 

 San Quintin suggest that gray whale feeding on 

 benthic invertebrates may be relatively common in 

 Baja California. If this hypothesis is accurate, 

 perhaps gray whales migrate to the southern lagoons 

 because of the availability of benthic prey, as well as 

 for the warm temperature and protection for calves. 

 Many whales occur at the entrances and outside the 

 calving lagoons where apparent feeding behavior 

 also has been observed (Norris et al. in press). 

 Although we were primarily concerned with bottom 

 communities within the lagoons, lagoon entrances 

 and offshore habitats were explored as well. 



Because stomach contents of gray whales are un- 

 available from recent years, we were unable to ex- 

 amine diets directly. Instead, we compared 

 populations of benthic prey in the Bering Sea with 

 the abundance and biomass of potential benthic prey 

 in San Quintin and five other lagoons of Baja Califor- 

 nia (three calving and two noncalving lagoons). In ad- 

 dition, we searched the calving and noncalving 

 lagoons for two important signs of gray whale feed- 

 ing: Benthic feeding excavations and fecal 

 material. 



METHODS 



Benthic invertebrate communities were surveyed in 

 six coastal lagoons of Baja California during January 

 1981 (Fig. 1). Laguna San Quintin is the most 

 northerly lagoon and is visited only infrequently by 

 gray whales. There is little or no gray whale activity in 

 Laguna Manuela and Estero Coyote, which are small 

 southern lagoons with shallow entrances and chan- 

 nels. Laguna Guerrero Negro, Ojo de Liebre (Scam- 

 mon' s Lagoon) , and San Ignacio are large lagoons and 

 major calving areas for gray whales. The other impor- 

 tant calving area, the complex of lagoons around 



Bahia Magdalena, was not surveyed in the present 

 study (Fig. 1). 



The six lagoons were surveyed by divers with and 

 without scuba. Because even the deeper lagoon chan- 

 nels are relatively shallow (often <10 m), bottom 

 communities were surveyed by skin divers without 

 scuba. Scuba was used to collect quantitative sam- 

 ples and to make more detailed observations of areas 

 of special interest. About 40% of the dive areas 

 shown in Figure 1 involved scuba. Each lagoon was 

 surveyed by two sets of divers from two small boats. 



Quantitative bottom samples were taken with 

 diver-held corers (0.0 18 or 0.0075 nr), washed over a 

 0.5 mm screen, and preserved in a solution of 4% for- 

 maldehyde. Samples were taken in three major 

 habitats: The central channel, eelgrass beds on the 

 channel edges, and unvegetated sandflats above the 

 eelgrass. Most benthic invertebrates were identified 

 to the lowest possible taxon, and wet weight of the to- 

 tal fauna from each core sample was recorded. The 



San Quintin (J6) 



Manuela®, 

 Guerrero Negro (32) 



Ojo de Liebre (JO)- 



Coyote GO 

 San lgnacio(6 



Bahia de 



Magdalena Complex 

 o too 



FIGURE 1. — Study sites along the Pacific coast of Baja California. 

 Number of survey dives indicated for each site. 



514 



