Eduardo Grimaldo

Pneumatic oil barriers: The promise of area bubble plumes

Reviews of bubble curtain oil herding studies in 1971 and in 1997 concluded that a bubble oil boom, or pneumatic oil barrier, is ineffective for retaining oil spills except in quiescent water, such as harbors. A bubble oil boom generates a sea-surface outwelling flow that traps or blocks oil. The primary bubble oil boom failure mode arises from oil droplet injection due to turbulence and instabilities at the oil slick front, where the outwelling flow balances the oil spreading. Bubble oil boom leakage occurs where these droplets are entrained into and pass through the bubble barrier. Increasing bubble flow creates stronger outwelling flows but increases turbulence and instabilities, leading to enhanced oil droplet entrainment. Natural seep observations, field trials, and laboratory studies demonstrate that a bubble plume with a wide bubble oil boom area, which is driven by an array of several parallel spargers (a bubble raft), can increase oil retention greatly while addressing key bubble oil boom failure modes compared with a line-source bubble curtain plume. Further improvements are identified by synergistic bubble oil boom application with a retaining skirt, dramatically improving the bubble oil boom performance. Specifically, the bubble oil boom keeps the oil distant from the skirt, minimizing or eliminating several conventional oil boom failure mechanisms. Also, entrained droplets, which easily traverse a single bubble curtain, are blocked effectively by a wide bubble plume curtain.

Commercial Exploitation of Zooplankton in the Norwegian Sea

Since 1990s there has been increased interest in the exploitation of marine zooplankton like copepods and krill. This has been motivated by the increasing demand for marine bioresources for human consumption in general, and in particular the growing demand for feed in aquaculture. In Nordic Seas, zooplankton is a key component in the energy transfer from primary producers to higher trophic levels such as herring, capelin, salmon, cod larvae and juveniles, and other species (Skjoldal, 2005). Roughly 70-80% of the zooplankton production in these waters is made up by copepods of the genus Calanus (Tande and Miller, 2000). According to general ecological theory about 10% of this production is available to the next trophic level (Lalli and Parsons, 1997). Estimates of the total annual production of Calanus sp. vary between 75 million tons y−1 for the Nordic Seas (Aksnes and Blindheim 1996) and 300 million tons Calanus sp. (mainly Calanus finmarchicus) y−1 for the Norwegian Sea only (Skjoldal et al. 2004).

Combination of a sorting grid and a square mesh panel to optimize size selection in the North-East Arctic cod (Gadus morhua) and redfish (Sebastes spp.) trawl fisheries

Combination of a sorting grid and a square mesh panel to optimize size selection in the North-East Arctic cod (Gadus morhua) and redfish (Sebastes spp.) trawl fisheries Manu Sistiaga*, Bent Herrmann, Eduardo Grimaldo, Roger B. Larsen, Leonore Olsen, Jesse Brinkhof, and Ivan Tatone SINTEF Ocean, Brattørkaia 17C, N-7010 Trondheim, Norway The Arctic University of Norway UIT, Hansine Hansens veg 18, 9019 Tromsø, Norway SINTEF Nord, Storgata 118, N-9008 Tromsø, Norway *Corresponding author: tel: þ479 166 3499; e-mail: manu.sistiaga@sintef.no.

Fishing efficiency of biodegradable PBSAT gillnets and conventional nylon gillnets used in Norwegian cod (Gadus morhua) and saithe (Pollachius virens) fisheries

Fishing efficiency of biodegradable PBSAT gillnets and conventional nylon gillnets used in Norwegian cod (Gadus morhua) and saithe (Pollachius virens) fisheries Eduardo Grimaldo*, Bent Herrmann, Jørgen Vollstad, Biao Su, Heidi Moe Føre, Roger B. Larsen, and Ivan Tatone SINTEF Ocean, Brattørkaia 17C, N-7010 Trondheim, Norway UiT, The Arctic University of Norway, Breivika, N-9037 Tromsø, Norway *Corresponding author: tel: þ 4740624014; e-mail: Eduardo.Grimaldo@sintef.no. The first two authors contributed equally to this work.

Trawl Selectivity in the Barents Sea Demersal Fishery

This chapter provides a general overview of the Barents Sea demersal trawl fishery. First, it reviews historical catch levels and current biomass status of four commercially important demersal species (cod, haddock, Greenland halibut, and redfish) and includes an overview of their management plan that has been carried out by the Joint Norwegian–Russian commission. Then, it presents the evolution of the technical regulations for improving size selectivity in this fishery and describes current challenges in gear selectivity. Later, this chapter describes the concept of size selectivity, introduces the selective parameters that define a selection curve, and progressively introduces different parametric models that describe the selection process. The most common experimental methods and gear used to collect selectivity data are described, and their advantages and disadvantages are discussed. Finally, this chapter describes an alternative, or a complementary method, to the conventional estimation of trawl selectivity—the FISHSELECT method. This method is based on morphology measurements and fish penetration models to estimate the selective properties of different mesh shapes and sizes at different mesh openings, which are later used to provide simulation-based prediction of size selectivity. FISHSELECT has already been applied to four important species of the Barents Sea Demersal Fishery, and the results have in all cases showed to be coherent with the results obtained from sea trial results.