Scientific, Technical and Economic Committee for Fisheries (STECF) Report of the SGMED-09-02 Working Group on the Mediterranean - Part I

SGMED-09-02 was held on 8-12 June 2009 in Sardinia (Italy). The report is a compilation of information on existing fisheries and stock data in order to update the status of the main demersal and small pelagic stocks. The report deals with assessment of historic and recent trends in stock parameters (stock size, recruitment and exploitation) and relevant scientific advice. STECF reviewed the report during its Plenary meeting on 9-13 November 2009.JRC.DG.G.4-Maritime affair

Scientific, Technical and Economic Committee for Fisheries (STECF) - Report of the SGMED-09-03 Working Group on the Mediterranean Part II

SGMED-09-03 meeting was held on 14-18 December 2009 in Barza d¿ Ispra (Italy). The report provides specific stock (by species and GSAs) predictions of stock size, fishing mortality and catches in short term (2009-2011) and medium term (2009-2018) under different management scenarios, for the main demersal and small pelagic Mediterranean stocks. STECF reviewed the report during its Plenary meeting on 26-30 April 2010 in Norwich.JRC.DG.G.4-Maritime affair

Spatially explicit stock assessment uncovers sequential depletion of northern shrimp stock components in the North Sea

Space is a critical component of fisheries management. Despite this, very few of the world's fish and shellfish stocks are currently assessed using methods that are spatially structured. In the Northeast Atlantic, northern shrimp in the North Sea and Skagerrak, is currently assessed using a spatially structured assessment model. This metapopulation model includes two spatial units (the Norwegian Deep and the Skagerrak), however, in the recent past, the fishery on northern shrimp in the North Sea also occurred in a third neighbouring fishing area, the Fladen Ground. Here, we have reconstructed the dynamics of northern shrimp in the Fladen Ground using historic landings, a standardized commercial index of abundance and fragmented survey data and integrated this third spatial unit into the assessment model of the stock. In doing so, we find evidence of sequential spatial depletion, whereby high rates of fishing mortality have successively eroded stock components in a west to east pattern of overexploitation and produced cryptic collapses. This finding is the first documented case of sequential spatial depletion in the Northeast Atlantic, a phenomenon that could be common and largely overlooked by stock assessment methods that are inherently non-spatial

Scientific, Technical and Economic Committee for Fisheries (STECF) - Report of the SGMED-08-04 Working Group on the Mediterranean Part IV

SGMED-08-04 was held on 6-10 October 2008 in Ponza (Italy). The meeting was the last of a series of four meetings convened in 2008 with the aim of strengthening scientific cooperation and improving scientific advice on the management of stocks of demersal and small pelagics in the Mediterranean. STECF reviewed the report during its Plenary meeting on 3-7 November 2008.JRC.G.4-Maritime affair

Sleeping Unsafely Tucked in to Conserve Energy in a Nocturnal Migratory Songbird

Each spring and fall, millions of normally diurnal birds switch to migrating at night. Most of these are small songbirds (passerine) migrating long distances that need to alternate their migratory flights with refueling stopovers [1,2], which can account for up to 80% of the total migratory period [3]. After a long nocturnal flight, these birds face the contrasting needs to recover sleep and refill depleted energy stores, all while vulnerable to predation [4,5]. Here, we investigated how garden warblers at a Mediterranean stopover site modulate their sleep behavior in relation to their metabolic state. At night, garden warblers in poor metabolic condition sleep more and exhibit less migratory restlessness than birds in good condition do. In addition, rather than sleeping with their head facing forward, birds in poor condition prefer to sleep with their head turned and tucked in their feathers. We further show that sleep with the head tucked is associated with lower respiratory and metabolic rates and reduced heat loss mediated by hiding the head—the body part with the highest heat dissipation—under the feathers. However, the benefit of conserving energy while sleeping with the head tucked was countered by reduced anti-predator vigilance. Birds presented with a sound simulating the approach of a predator responded more slowly when the head was tucked than when it was untucked. Consequently, our study demonstrates that through changing their sleep position and intensity, migrating songbirds can negotiate a previously unknown trade-off between sleep-mediated energy conservation and anti-predatory vigilance

Energy stores, oxidative balance and sleep in migratory Garden Warblers (Sylvia borin) and Whitethroats (Sylvia communis) at a spring stopover site

Little is known about how songbirds modulate sleep during migratory periods. Due to the alternation of nocturnal endurance flights and diurnal refueling stopovers, sleep is likely to be a major constraint for many migratory passerine species. Sleep may help to increase the endogenous antioxidant capacity that counteracts free radicals produced during endurance flight and reduces energy expenditure. Here, we investigated the relationship between sleep behavior, food intake, and two markers of physiological condition—the amount of energy reserves and oxidative status—in two migratory songbird species, the garden warbler (Sylvia borin) and the whitethroat (Sylvia communis). In garden warblers, birds with high energy stores were more prone to sleep during the day, while this condition-dependent sleep pattern was not present in whitethroats. In both species, birds with low energy stores were more likely to sleep with their head tucked in the feathers during nocturnal sleep. Moreover, we found a positive correlation between food intake and the extent of energy reserves in garden warblers, but not in whitethroats. Finally, we did not find significant correlations between oxidative status and sleep, or oxidative status and energy stores. Despite our study was not comparative, it suggests that different species might use different strategies to manage their energy during stopover and, additionally, it raises the possibility that migrants have evolved physiological adaptations to deal with oxidative damage produced during migration