A new species of the mud shrimp genus Axianassa Schmitt, 1924 (Decapoda: Gebiidea: Laomediidae) from the Ryukyu Islands, southern Japan

A new species of the laomediid mud shrimp genus Axianassa Schmitt, 1924, A. planioculus, is described and illustrated on the basis of a single male specimen from intertidal muddy sand flat of Kabira Bay, Ishigaki Island, southern Ryukyu Islands, Japan. Axianassa planioculus n. sp. is morphologically closest to A. mineri Boone, 1931, known from Pacific Panama, among the 11 known congeners, but is readily distinguished from the latter by the eyes being dorsally concealed by the rostrum, the subovate telson, the unarmed carpus of the maxilliped 3 and the unarmed uropodal endopod. The discovery of a new mud-shrimp species in an easily accessible habitat indicates that the shallow-water infaunal decapods are still relatively poorly known. A partial segment of the mitochondrial 16S rRNA gene was sequenced from the holotype for future genetic studies.

Dispersal and productivity of Chinook (Oncorhynchus tshawytscha) and coho (Oncorhynchus kisutch) salmon colonizing newly accessible habitat

Following construction of a fish ladder at Landsburg Diversion Dam on the Cedar River, Washington, USA, in fall 2003, we used DNA-based parentage to identify second generation Chinook (Oncorhynchus tshawytscha) and coho (Oncorhynchus kisutch) salmon as recruits that were produced above the dam or “strays” dispersing into the new habitat that were produced elsewhere. For both species, strays colonized immediately but decreased as a proportion of the total run over time. Chinook salmon strays were more numerous in years when the species was more abundant below the dam and included a much larger proportion of hatchery origin salmon than did coho salmon. Productivity, calculated as the ratio of female recruits sampled at the dam to female spawners, exceeded replacement in all four coho salmon cohorts but only two of five Chinook salmon cohorts, leading to more rapid population expansion of coho salmon. However, estimates of fishing mortality and recruitment into the Cedar River below the dam substantially increased Chinook salmon productivity estimates. Our results demonstrate that Pacific salmon are capable of rapidly recolonizing habitat made accessible by restoration and emphasize the importance of demographic exchange with preexisting populations during the transition from recolonization to self-sustainability.

Movements of adult coho salmon (Oncorhynchus kisutch) during colonization of newly accessible habitat

Pacific salmon (Oncorhynchus spp.) have repeatedly exploited new habitat following glacial recession and some artificial introductions, yet the initial process of colonization is poorly understood. Landsburg Diversion Dam on the Cedar River, Washington, excluded salmon from 33 km of habitat for over a century until it was modified to allow passage in 2003. Adult coho salmon (Oncorhynchus kisutch) were sampled as they entered the newly accessible habitat in the first 3 years and a subset received radio transmitters to assess spawning site selection and movement. Annual counts of coho colonists increased over time, and in 2 of 3 years, daily dam passage was positively correlated with river discharge. Contrary to our prediction that coho would spawn in tributaries, all identified spawning sites were in the mainstem Cedar River, though 38% of radio-tagged salmon entered a tributary at least temporarily. Females moved little within the new habitat (average = 5.8 km), whereas males moved extensively (average = 34.8 km), especially when females were scarce. The immediate use of the new habitat by colonists and their widespread movements suggest that exploration is an innate component of salmon breeding behavior, and restoring access to lost habitat merits prioritization as a conservation strategy.

Leslibetaeus coibita, n. gen., n. sp., a new alpheid shrimp from the Pacific coast of Panama (Crustacea: Decapoda)

A new alpheid shrimp, Leslibetaeus coibita, n. gen., n. sp., is described on the basis of two specimens extracted from crevices in a shale rock on the rocky intertidal shore in the Isla Coiba National Park, Pacific coast of Panama. Leslibetaeus is characterized by absence of rostrum and orbital teeth; eyes being only partially covered by carapace; sixth abdominal somite without articulated plate; first segment of the antennular peduncle without tooth on ventromesial carina; short scaphocerite; tip of third maxilliped with stout spines; and strap-like epipods present on third maxilliped and first to fifth pereiopod; stout symmetrical chelipeds, with carpus distally strongly lobed and bearing two rows of setae mesially, and chela without snapping mechanism; carpus of second pereiopod five-segmented, with second segment distinctly longer than first; ischium and merus of third pereiopod unarmed. The new genus appears to be relatively basal and not closely related to any of the currently described alpheid genera. The finding of this new taxon in a relatively accessible habitat indicates a yet unexplored biological potential of the Isla Coiba National Park.