Seasonal and ephemeral color patterns in the kelp bass, Paralabrax clathratus, were studied on Santa Catalina Island, California from April 2000 to September 2002. Adults were monochromatic for part of the year (calico phase) and sexually dichromatic from April to October, with most adult males adopting bright orange snouts (OS phase). The seasonal occurrence of the OS phase in males overlapped with the spawning season, and the color was limited to ripe males. The OS phase in ripe males may function as a signal of sexual identity and sexual readiness to females. Both males and females exhibited distinct color patterns during courtship and spawning periods. During these periods, males were charcoal colored with dark black bars overlaying white spots (checkered phase), and females were often black with no visible spots (dark phase). Color patterns displayed by adults during spawning activities may facilitate mate signaling and the formation of spawning groups. Specific color patterns were also observed in relation to habitat and aggressive behaviors.

The conspicuous and cryptic fish assemblage of the Los Angeles Federal Breakwater was assessed from 2002 to 2003. Thirty-five species were observed or collected during the study period. The assemblage of cryptic fishes was composed primarily of a mix of Oregonian and San Diegan, species including snubnose sculpin (Orthonopias triacis), coralline sculpin (Artedius corallinus) and blackeye goby (Rhinogobiops nicholsii). The species composition of conspicuous fishes was approximately equal between taxa from these two provinces. Blacksmith (Chromis punctipinnis), black perch (Embiotoca jacksoni) and kelp bass (Paralabrax clathratus) dominated the assemblage of conspicuous fishes. Species composition reflects the localized cool temperature regime of the area and the high relief kelp forest habitat.

The diversity patterns of the polychaete fauna from a Pacific coastal lagoon were described. Polychaetes were collected in 1995 and 1998. This lagoon is formed by 2 arms: the western arm named Bahia Falsa and the eastern arm named Bahia San Quintin. 46 stations were sampled with a geological box corer. A total of 3,275 polychaetes, 28 families, 56 genera, and 104 species were identified in 1995, and 3,168 polychaetes were collected in 1998, 21 families, 39 genera and 65 species. From all the macrofauna collected in both surveys, polychaetes represented 45.2%. From the species collected, 55% correspond to new records for the area. Families Dorvilleidae, Polynoidae, Oweniidae, Scalibregmatidae, Sternapsidae and Sigalionidae present in 1995, were not in 1998 survey.

The stations with higher abundances: (> 100 specimens/0.02 m²) were located on the southern half of Bahia San Quintin. Species richness and diversity were also higher in San Quintin Bay. From the 30 families previously reported for San Quintin lagoon, 23 have been collected and 6 families were added: Ampharetidae, Oweniidae, Scalibregmatidae, Sternapsidae, Dorvilleidae and Sigalionidae. Families not found in both surveys were: Paraonidae, Magelonidae, Apistobranchidae, Sphaerodoridae, Trichobranchidae, Chrysopetalidae and Arenicolidae.

Results showed slightly lower redox potential values (−336 to 187 mV), slightly higher sediment temperatures (19.8°–22.1°C) and organic matter contents (0.3–4.1%) in 1998.

From 1995 to 1998 a change in the composition and structure of the polychaete communities was noted; species richness diminished from 104 to 65 species. The trophic complexity changed with an increase of deposit-feeders, the abundance of other trophic categories decreased, indicating a loss of complexity. Significant changes in the abundance of some families were detected, some increased their abundances: Spionidae from 17% to 48%, Orbiniidae from 4% to 13%; other families decreased in terms of abundance and number of species: Lumbrinereidae from 11% to 1.4%, Nereididae from 9% to 1% and Sabellidae from 14% to 5%. These modifications altered the composition and structure of the polychaete communities in this lagoon. Increased anthropogenic disturbance (oyster culture, agriculture) and environmental variability due to the ENSO 97–98 may have affected recruitment and survival of some polychaete species.

The epifaunal community associated with eelgrass beds in San Quintin Bay, Baja California, Mexico, was studied from April to November 1993. Taxonomic identification, univariate community descriptors, and biomass data were obtained for each sample. Multivariate analyses of community composition were also performed, and plant–animal relationships were analyzed. The epifaunal community was characterized by the high abundance of a few dominant species, with the mollusk Assiminea dubiosa representing 70% of the total abundance. Summer samples had the highest similarity, as indicated by the Analysis of Similarity (ANOSIM) test. Polychaetes and amphipod abundances seemed to follow the variations in eelgrass aboveground biomass.