No abstract

Mussels, clams, and tube worms collected in the vicinity of hydrocarbon seeps on the Louisiana slope contain mostly "dead" carbon, indicating that dietary carbon is largely derived from seeping oil and gas. Enzyme assays, elemental sulfur analysis, and carbon dioxide fixation studies demonstrate that vestimentiferan tube worms and three clam species contain intracellular, autotrophic sulfur bacterial symbionts. Carbon isotopic ratios of 246 individual animal tissues were used to differentiate heterotrophic (8(13)C = -14 to -20 per mil), sulfur-based (8(13)C = -30 to -42 per mil), and methane-based (8(13)C = <-40 per mil) energy sources. Mussels with symbiotic methanotrophic bacteria reflect the carbon isotopic composition of the methane source. Isotopically light nitrogen and sulfur confirm the chemoautotrophic nature of the seep animals. Sulfur-based chemosynthetic animals contain isotopically light sulfur, whereas methane-based symbiotic mussels more closely reflect the heavier oceanic sulfate pool. The nitrogen requirement of some seep animals may be supported by nitrogen-fixing bacteria. Some grazing neogastropods have isotopic values characteristic of chemosynthetic animals, suggesting the transfer of carbon into the background deep-sea fauna.

[1] Reports of hypoxic conditions (oxygen <1.5 ml L −1 ) off the U.S. west coast over the last two decades led us to investigate hypoxia in the Southern California Bight (SCB) and its potential impacts on fisheries. The secular trend in hypoxia in the SCB over the last 57 years is not monotonic, and reversed trend in the mid-1980s, bringing oxygen concentrations back to levels measured in the late 1950s to early 1960s. Thirty-seven percent of the rockfish (Sebastes spp.) habitat in the Cowcod Conservation Area at 240-350 m depths suffers exposure to hypoxia in the summer of normal years. If current trends in shoaling of low oxygen water continue for another 20 years, rather than reversing as happened previously, we predict loss of 18% of the habitat with 55% of the total habitat exposed to hypoxia.

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The copper rockfish (Sebastes caurinus) is a benthic, nonmigratory, rocky reef species with pelagic larval and juvenile stages lasting several months. Adults are commonly distributed in temperate coastal waters of the Pacific Ocean from British Columbia to southern California, including the inland waterways of Puget Sound, Washington, a semi-enclosed fjord system of known postglacial origin. Here, we report the distribution of genetic variation at six microsatellite DNA loci from six locations throughout the species' range. Among four coastal samples, significant population subdivision was detected (FST = 0.007), and a significant correlation between genetic and geographic distance was observed. Divergence was large and significant between Puget Sound proper and coastal samples (FST = 0.087). A sample taken only 100 km north of Puget Sound (the Canadian Gulf Islands) was also highly divergent from Puget Sound and coastal samples and was genetically intermediate between the two. The Puget Sound sample also displayed significantly lower allelic diversity and a more substantial presence of private alleles. The patterns of genetic divergence and diversity are most consistent with a historical colonization followed by limited oceanographic exchange among geographically proximate locations.

The study of the early life history of large, open-ocean pelagic fishes such as tunas and billfish, and the identification of spawning and nursery habitats, has been extremely difficult as these animals are intrinsically rare, highly migratory, and difficult to study in captivity. Traditional methods such as the assembling of a developmental series of life stages, or the culturing of unknown eggs and larvae to a point where they can be identified, has not been easy or fruitful for many pelagic species. The discovery of a putative spawning 'hot spot' off the Kona coast of Hawaii, coupled with the development of shipboard approaches to real time identification and adaptive sampling of eggs, may provide new approaches and insights into the spawning ecology and reproductive biology of these highly valuable but poorly known species. Here we report the use of a shipboard PCR based assay to differentiate species of istiophorid billfish larvae and identify eggs of istiophorid and xiphiid billfish, coryphaenid dolphinfish, and wahoo. A species-specific multiplex PCR assay was designed to amplify a single, unique size fragment of the mitochondrial cytochrome b gene for all 6 species of Indo-Pacific billfish, both dolphinfish, and the monospecific wahoo. A boiling technique used to extract DNA from larval eye tissue or an individual egg, combined with a single-step PCR assay and agarose electrophoresis, allowed species identification within 3 h of sample acquisition. This nearly real-time identification method for morphologically indistinguishable eggs and larvae provides an opportunity to employ adaptive sampling methods to increase sampling efficiency and will help in determining the spatial and temporal dimensions of spawning and nursery habitats offshore. This study describes the occurrence of blue marlin, dolphinfish, shortbill spearfish, swordfish and wahoo off the Kona coast by molecular approaches, and it provides the first description of the eggs of blue marlin, shortbill spearfish and wahoo.

No abstract

A recent phylogenetic review of the genus Sebastes suggested the existence of a cryptic species of vermilion rockfish (Sebastes miniatus). To evaluate the geographical and bathymetric range of the Type 1 and Type 2 forms reported in that study, cytochrome b sequences were examined from 548 fish. Type 1 fish were found primarily south of Point Conception on reefs deeper than 100 m. Type 2 fish were common range-wide at sites shallower than 100 m. Reproductive isolation between the two types was tested using nine microsatellite loci. Estimates of genetic divergence were made using the fixation index (F(ST)) and correspondence between haplotype and genotype was tested by Bayesian population assignment and multivariate plotting of individual genotypes. Microsatellite analyses gave strong support for the presence of two distinct groups of genotypes. All fish with Type 1 haplotypes and fish with Type 2 haplotypes from < 100 m depth had genotypes unique to their haplotype group. However, most (68%) fish with Type 2 haplotypes from > 100 m depth assigned strongly to the Type 1 genotype group. Morphometric comparisons between the two genotypic groups revealed significant differences at three of the six examined measurements. Differences in both genetics, depth of occurrence, and morphology suggest these are separate species. This observation along with evidence of depth segregation in many recent species pairs led us to hypothesize a speciation model for Sebastes spp. by which the loss or truncation of a depth-related ontogenetic migration can lead to the creation of reproductively isolated populations.