In the Atlantic, economic losses have been reported from shark, swordfish and tuna longline fisheries due to depredation by cetaceans. We examined interactions of odontocete cetaceans with commercial longliners operating in waters off Brazil and the Azores archipelago during 2006-2007, analysing relationships between catches, depredation on hooked fish, cetacean sightings, acoustic records of cetacean presence and environmental variables. Data were provided by skippers of six vessels and by onboard observers for two vessels. The percentage of longline sets depredated by cetaceans was low (ranging from 1% to 9% of total sets per ship) but the proportion of fish damaged was high (up to 100%) when depredation occurred. Catches were related to the phase of the moon, cloud cover, sea surface temperature and water depth whereas cetacean sightings were primarily related to catches. In particular there was a positive association between Delphinus delphis sightings and catches of swordfish, and between Stenella frontalis sightings and mako catches. Acoustic detection was low when depredation by false killer whales occurred although high rates of clicks were detected when delphinids were sighted and false killer whales were by-caught. This may indicate that false killer whales are not echolocating when feeding on fish hooked on a longline.

This study provides a first approach concerning a novel chilling strategy, which employs a mixture of different preservative organic acids (ascorbic, citric and lactic) in the icing medium. Thus, ice prepared from water including two different concentrations of a commercial acid mixture-formula (800 and 400 ppm; C-800 and C-400 conditions, respectively) were applied as icing system to three important commercial fish lean species (hake, Merluccius merluccius; megrim, Lepidorhombus whiffiagonis; angler, Lophius piscatorius). Lipid oxidation (peroxide value; thiobarbituric acid index; fluorescent compound formation) and hydrolysis (free fatty acid formation) were evaluated throughout the chilling time (up to 12-15 days) and compared to results obtained in fish kept under traditional ice prepared only from water (C-0 condition); a complementary sensory evaluation was carried out. As a result of employing the C-800 icing condition, a partial inhibition of lipid oxidation and hydrolysis development was obtained that was accompanied by a shelf life enhancement in all cases. Further research taking into account the complementary action of the present organic acids is envisaged. According to the lipid damage analysis, lipid hydrolysis was a more relevant event than lipid oxidation in all fish species tested.

a b s t r a c tNatural preservative organic acids (ascorbic, citric and lactic acids) were used to prepare a novel organic acid-flake icing system for the chilled preservation of hake (Merluccius merluccius), megrim (Lepidorhombus whiffiagonis) and angler (Lophius piscatorius). The icing system was prepared with two different concentrations of a commercial acid mixture-formula containing the three organic acids at 800 mg/kg and 400 mg/kg (C-800 and C-400 batches, respectively). Aerobic mesophiles, psychrotrophs, proteolytic bacteria, trimethylamine and pH were evaluated and the results compared with sensory analyses. Significantly (P < 0.05) lower counts of mesophiles were found for hake and megrim in the C-800 and C-400 batches compared with the control batch. In the case of angler, significantly (P < 0.05) lower counts of mesophiles, psychrotrophs and proteolytic microorganisms (P < 0.05) were found for fish stored in the C-800 icing conditions. Both C-400 and C-800 megrim batches exhibited significantly (P < 0.05) lower pH values than the control batch, and this result was also observed in the C-800 angler batch. Sensory analysis confirmed that the shelf lives of the three fish species in the C-800 batch were extended. According to the parameters assessed, storage of hake, megrim and angler in the proposed ice system better protects their microbial and sensory qualities.

Quality loss inhibition in chilled blue whiting (Micromesistius poutassou) was investigated. For it, a natural organic acid-mixture including ascorbic, citric and lactic acids was applied in a two-step processing strategy: (i) as an aqueous dipping medium previous to chilling storage and, (ii) included in the flake ice employed as chilling system. As a result of the acid-mixture addition, a partial inhibition of microbial and biochemical mechanisms involved in the quality loss was obtained. Thus, aerobe and psychrotrophe counts in treated fish showed lower ranges (2.07-4.15 and 2.43-4.39 log CFU g )1 , respectively) than control fish (2.64-5.83 and 2.30-5.30 log CFU g )1 , respectively). Sensory analysis revealed that treated fish was still acceptable at the end of the experiment (day 9), while control fish was rejected at this time. Lipid hydrolysis (free fatty acid formation) proved to be more limiting of fish quality than lipid oxidation (peroxide and thiobarbituric acidreactive substance formation).

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