Lessons learned from practical approaches to reconcile mismatches between biological population structure and stock units of marine fish

Recent advances in the application of stock identification methods have revealed inconsistencies between the spatial structure of biological populations and the definition of stock units used in assessment and management. From a fisheries management perspective, stocks are typically assumed to be discrete units with homogeneous vital rates that can be exploited independently of each other. However, the unit stock assumption is often violated leading to spatial mismatches that can bias stock assessment and impede sustainable fisheries management. The primary ecological concern is the potential for overexploitation of unique spawning components, which can lead to loss of productivity and reduced biodiversity along with destabilization of local and regional stock dynamics. Furthermore, ignoring complex population structure and stock connectivity can lead to misperception of the magnitude of fish productivity, which can translate to suboptimal utilization of the resource. We describe approaches that are currently being applied to improve the assessment and management process for marine fish in situations where complex spatial structure has led to an observed mismatch between the scale of biological populations and spatially-defined stock units. The approaches include: (i) status quo management, (ii) "weakest link" management, (iii) spatial and temporal closures, (iv) stock composition analysis, and (v) alteration of stock boundaries. We highlight case studies in the North Atlantic that illustrate each approach and synthesize the lessons learned from these real-world applications. Alignment of biological and management units requires continual monitoring through the application of stock identification methods in conjunction with responsive management to preserve biocomplexity and the natural stability and resilience of fish species.</p

Occurrence, distribution and abundance of cetaceans in Onslow Bay, North Carolina, USA

In this paper the occurrence, distribution and abundance of cetaceans in offshore waters of Onslow Bay, North Carolina, USA is described. Between June 2007 and June 2010 monthly aerial and shipboard line-transect surveys were conducted along ten 74km transects placed perpendicular to the shelf break. In total 42,676km of aerial trackline (218 sightings) and 5,209km of vessel trackline (100 sightings) were observed. Seven species of cetaceans were observed, but the fauna was dominated strongly by common bottlenose and Atlantic spotted dolphins. Both species were present year-round in the study area. Using photo-identification techniques, five bottlenose dolphins and one spotted dolphin were resighted during the three-year period. In general, the abundance of cetaceans in Onslow Bay was low and too few sightings were made to estimate monthly abundances for species other than bottlenose and spotted dolphins. Maximum monthly abundances of bottlenose and spotted dolphins were 4,100 (95% CI: 1,300–9,400) in May 2010 and 6,000 (95% CI: 2,500–17,400) in March 2009, respectively. Bottlenose dolphins were found throughout the study area, although they were encountered most frequently just off the shelf break. In contrast, spotted dolphins exhibited a strong preference for waters over the continental shelf and were not encountered beyond the shelf break.Publisher PDFPeer reviewe

Oil source rock potential of the lacustrine Jurassic Sim Uuju Formation, West Korea Bay Basin. Part II. Nature of the organic matter and hydrocarbon-generation history

The offshore West Korea Bay (WKB) Basin is one of a series of NE-SW rift basins which formed in Korea and eastern China over thin continental crust during the Late Mesozoic and Early Cenozoic, and is characterised by a two-layered structure - a Cenozoic basin is superposed on a pre-Tertiary basin. In Part I of this paper (Massoud et al., 1991), paraffinic oils recovered from Mesozoic and Tertiary sandstone intervals were found to have been generated from different source beds. Also, a probable thick (400-500 m) Jurassic source bed for the Mesozoic oil was geochemically identified in the basinal offshore area of the lacustrine Sim Uuju sequence penetrated by Well 606. In this Paper, the Authors complete the hydrocarbons survey on the formation by studying the type, amount and maturity of organic matter present, and the history of hydrocarbon generation. They conclude that the Jurassic bed could be considered as a major source for the Mesozoic oil in the WWB Basin, provided that it is of a sufficient extent to have produced large volumes of oil

Introduction or reintroduction? Last resorts for the latest bird to become extinct in Europe, the Andalusian hemipode Turnix sylvatica sylvatica

The Andalusian hemipode (Turnix sylvatica sylvatica) (Order: Turniciformes, Family: Turnicidae), formerly distributed in several Mediterranean countries, is a critically endangered bird, if not already extinct. Subspecies of the T. sylvatica complex, in turn composed by nine subspecies are widely distributed in Africa and southern Asia. The last free-ranging Andalusian hemipodes were shot by hunters near Donana National Park (Spain) in 1981. Therefore, this species could be the last bird species getting extinct in Iberia and Europe in the XXth century. This investigation deals with the phylogenetic relationships of the Andalusian hemipode with the sup- posedly congeneric T. varia, T. tanki, T. suscitator and T. pyrrhothorax, and with the supposedly conspecific T. sylvatica lepurana, which is the geographically nearest buttonquail population (occurring in central and southern Africa). A 606 bp long fragment of the cytochrome b gene (approx. 1140 bp) of the mitochondrial DNA was sequenced, using both museum skins (the only available source for T. s. sylvatica) or blood/tissue samples from contemporary individuals (remaining species and subspecies). Seven haplotypes were found: two each for T. varia and T. s. lepurana, and one each for T. tanki, T. suscitator, T. pyrrhothorax, and T. s. sylvatica. Sequence divergence values obtained from pairwise distances between the T. sylvatica group haplotypes and the other species, ranged from 19.4 to 25.9%. The low genetic divergence between T. s. sylvatica and T. s. lepurana (0.00–0.01%) confirmed that the current classification based on morphological characters is correct, and that these two taxa may should be considered as subspecies. This close relationship would permit an introduction T. sylvatica where the species was last seen in Spain (i.e., Donana National Park). This area is now strictly protected and human persecution is no longer a problem.Peer reviewe