Variations in abiotic conditions across large latitudinal gradients can strongly influence the early life history of coastal marine organisms. We investigated the effects of temperature and latitude on the larval traits of 2 estuarine fish species. The arrow goby Clevelandia ios and the endangered tidewater goby Eucyclogobius newberryi were studied in 18 estuaries along the coast of California, spanning ~8 degrees of latitude. These 2 species were selected because of their dissimilar preferences for estuary type: the arrow goby prefers cooler, fully tidal systems, whereas the tidewater goby prefers warmer lagoons that experience some degree of seasonal isolation from the ocean. Recently settled individuals were collected from July to October 2011, and temperatures within each estuary were recorded to determine how temperature affected larval duration, settlement, and growth rates. Temperatures were more variable among estuaries inhabited by the tidewater goby (10°C range) than among those inhabited by the arrow goby (5°C range). Larval traits of both species differed among sites, but more so for the tidewater goby, a difference that was tied to the greater differences in temperatures among sites in the seasonally closed estuaries it inhabited. In both species, fish that experienced warmer temperatures had shorter larval durations and faster growth rates and were smaller at settlement. Since the length of the larval period has been related to survival and dispersal distance, future variations in temperature due to climate change could have predictable influences on population density and connectivity in estuarine species.
A geographically isolated set of southern localities of the formerly monotypic goby genus Eucyclogobius is known to be reciprocally monophyletic and substantially divergent in mitochondrial sequence and nuclear microsatellite-based phylogenies relative to populations to the north along the California coast. To clarify taxonomic and conservation status, we conducted a suite of analyses on a comprehensive set of morphological counts and measures from across the range of Eucyclogobius and describe the southern populations as a new species, the Southern Tidewater Goby, Eucyclogobius kristinae, now separate from the Northern Tidewater Goby Eucyclogobius newberryi (Girard 1856). In addition to molecular distinction, adults of E. kristinae are diagnosed by: 1) loss of the anterior supratemporal lateral-line canals resulting in higher neuromast counts, 2) lower pectoral and branched caudal ray counts, and 3) sets of measurements identified via discriminant analysis. These differences suggest ecological distinction of the two species. Previous studies estimated lineage separation at 2–4 million years ago, and mitochondrial sequence divergence exceeds that of other recognized fish species. Fish from Santa Monica Artesian Springs (Los Angeles County) northward belong to E. newberryi; those from Aliso Creek (Orange County) southward constitute E. kristinae. The lagoonal habitat of Eucyclogobius has been diminished or degraded, leading to special conservation status at state and federal levels beginning in 1980. Habitat of the newly described species has been impacted by a range of anthropogenic activities, including the conversion of closing lagoons to open tidal systems in the name of restoration. In the last 30 years, E. kristinae has only been observed in nine intermittently occupied lagoonal systems in northern San Diego County; it currently persists in only three sites. Thus, the new species is in imminent danger of extinction and will require ongoing active management.
for their help gaining access to study sites, collections, and project logistics. Thanks to Larry Allen, Camm Swift, David Jacobs, and Steve Dudgeon for their wealth of knowledge and project guidance. We appreciate the help of Aaron Dufault in collecting fish, and Brian Peña and Rando Has for their long hours spent in the lab dissecting fish and preparing otoliths. This project was supported by the
The fringing reefs in Opunohu Bay and Cook’s Bay in Moorea, French Polynesia are an important component of Moorea’s fringing reef system, as they comprise approximately 20% of the island’s perimeter. The two bays are assumed to have differing benthic communities due to differences in onshore land development and freshwater input, but observational studies of their benthic communities are rarely published. To address this information gap, we conducted a quadrat-based benthic survey to determine important drivers of coral spatial variation throughout the bays. Interestingly, we found that coral taxonomic richness and cover did not significantly vary between bays, and corals only declined at the sites nearest freshwater input. Instead, coral richness was significantly greater when the territorial herbivorous damselfish Stegastes nigricans was present. The majority of the corals we documented were relatively small (88% < 10 cm diameter), thus our results support a positive effect of S. nigricans on young coral diversity. Stegastes nigricans could potentially be creating a refuge inside their territories from scraper herbivores for many non-dominant corals, although other potential mechanisms and the context of these benefits warrant further investigation. We conclude that, on the fringing reefs of Moorea’s two major bays, spatial variation in coral richness is more strongly associated with patches of S. nigricans territories than larger-scale differences in onshore land development and distance from freshwater input.
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