Decision analysis applied to the fishery of the sea snail Concholepas concholepas from central northern coast of Chile

Formal decision analysis was applied to the management of loco (Concholepas concholepas, Fam. Muricidae) in Chile, 29-35 degrees S. Four interested groups were considered "Fishers", "Scientists", "Buyers" and the "State", along with three fishing effort levels and four subobjectives. The method was found to encourage the emergence of a consensus (here: halving of effort), and is recommended for use in other fisheries.

Analysis of permanent magnets as elasmobranch bycatch reduction devices in hook-and-line and longline trials

Previous studies indicate that elasmobranch fishes (sharks, skates and rays) detect the Earth’s geomagnetic field by indirect magnetoreception through electromagnetic induction, using their ampullae of Lorenzini. Applying this concept, we evaluated the capture of elasmobranchs in the presence of permanent magnets in hook-and-line and inshore longline fishing experiments. Hooks with neodymium-iron-boron magnets significantly reduced the capture of elasmobranchs overall in comparison with control and procedural control hooks in the hook-and-line experiment. Catches of Atlantic sharpnose shark (Rhizoprionodon terraenovae) and smooth dogfish (Mustelus canis) were signif icantly reduced with magnetic hook-and-line treatments, whereas catches of spiny dogfish (Squalus acanthias) and clearnose skate (Raja eglanteria) were not. Longline hooks with barium-ferrite magnets significantly reduced total elasmobranch capture when compared with control hooks. In the longline study, capture of blacktip sharks (Carcharhinus limbatus) and southern stingrays (Dasyatis americana) was reduced on magnetic hooks, whereas capture of sandbar shark (Carcharhinus plumbeus) was not affected. Teleosts, such as red drum (Sciaenops ocellatus), Atlantic croaker (Micropogonias undulatus), oyster toadfish (Opsanus tau), black sea bass (Centropristis striata), and the bluefish (Pomatomas saltatrix), showed no hook preference in either hook-and-line or longline studies. These results indicate that permanent magnets, although eliciting species-specific capture trends, warrant further investigation in commercial longline and recreational fisheries, where bycatch mortality is a leading contributor to declines in elasmobranch populations.

Population structure of chum salmon (Oncorhynchus keta) across the Pacific Rim, determined from microsatellite analysis

The Pacific Rim population structure of chum salmon (Oncorhynchus keta) was examined with a survey of microsatellite variation to describe the distribution of genetic variation and to evaluate whether chum salmon may have originated from two or more glacial refuges following dispersal to newly available habitat after glacial retreat. Variation at 14 microsatellite loci was surveyed for over 53,000 chum salmon sampled from over 380 localities ranging from Korea through Washington State. An index of genetic differentiation, FST, over all populations and loci was 0.033, with individual locus values ranging from 0.009 to 0.104. The most genetically diverse chum salmon were observed from Asia, particularly Japan, whereas chum salmon from the Skeena River and Queen Charlotte Islands in northern British Columbia and those from Washington State displayed the fewest number of alleles compared with chum salmon in other regions. Differentiation in chum salmon allele frequencies among regions and populations within regions was approximately 18 times greater than that of annual variation within populations. A regional structuring of populations was the general pattern observed, with chum salmon spawning in different tributaries within a major river drainage or spawning in smaller rivers in a geographic area generally more similar to each other than to populations in different major river drainages or geographic areas. Population structure of chum salmon on a Pacific Rim basis supports the concept of a minimum of two refuges, northern and southern, during the last glaciation, but four possible refuges fit better the observed distribution of genetic variation. The distribution of microsatellite variation of chum salmon on a Pacific Rim basis likely reflects the origins of salmon radiating from refuges after the last glaciation period.

Evolution of the tectogene concept, 1930-1965

The tectogene, or crustal downbuckle, was proposed in the early 1930s by F.A. Vening Meinesz to explain the unexpected belts of negative gravity anomalies in island arcs. He attributed the isostatic imbalance to a deep sialic root resulting from the action of subcrustal convection currents. Vening Meinesz's model was initially corroborated experimentally by P.H. Kuenen, but additional experiments by D.T. Griggs and geological analysis by H.H. Hess in the late 1930s led to substantial revision in detail. As modified, the tectogene provided a plausible model for the evolution of island arcs into alpine mountain belts for another two decades. Additional revisions became necessary in the early 1950s to accommodate the unexpected absence of sialic crust in the Caribbean and the marginal seas of the western Pacific. By 1960 the cherished analogy between island arcs and alpine mountain belts had collapsed under the weight of the detailed field investigations by Hess and his students in the Caribbean region. Hess then incorporated a highly modified form of the tectogene into his sea-floor spreading hypothesis. Ironically, this final incarnation of the concept preserved some of the weaker aspects of the 1930s original, such as the ad hoc explanation for the regular geometry of island arcs.

Yield- and biomass-per-recruit analysis for rotational fisheries, with an application to the Atlantic sea scallop (Placopecten magellanicus)

A general model for yield-per-recruit analysis of rotational (periodic) fisheries is developed and applied to the sea scallop (Placopecten magellanicus) fishery of the northwest Atlantic. Rotational fishing slightly increases both yield- and biomass-per-recruit for sea scallops at FMAX. These quantities decline less quickly when fishing mortality is increased beyond FMAX than when fishing is at a constant rate. The improvement in biomass-per-recruit appears to be nearly independent of the selectivity pattern but increased size-at-entry can reduce or eliminate the yield-per-recruit advantage of rotation. Area closures and rotational fishing can cause difficulties with the use of standard spatially averaged fishing mortality metrics and reference points. The concept of temporally averaged fishing mortality is introduced as one that is more appropriate for sedentary resources when fishing mortality varies in time and space.

Report of the training in database and spatial analysis for Marine Protected Areas staff in Indonesia's BOBLME region, Medan, Indonesia, 30 June-4 July, 2015

Training included: Geographic Information System (GIS)concept and software; Global Positioning System (GPS); Ecological Gap Analysis and Marine Protected Area (MPA) design using Marine Reserve Design using Spatially Explicit Annealing (MARXAN); and cartography.