[1] Reports of hypoxic conditions (oxygen <1.5 ml L −1 ) off the U.S. west coast over the last two decades led us to investigate hypoxia in the Southern California Bight (SCB) and its potential impacts on fisheries. The secular trend in hypoxia in the SCB over the last 57 years is not monotonic, and reversed trend in the mid-1980s, bringing oxygen concentrations back to levels measured in the late 1950s to early 1960s. Thirty-seven percent of the rockfish (Sebastes spp.) habitat in the Cowcod Conservation Area at 240-350 m depths suffers exposure to hypoxia in the summer of normal years. If current trends in shoaling of low oxygen water continue for another 20 years, rather than reversing as happened previously, we predict loss of 18% of the habitat with 55% of the total habitat exposed to hypoxia.

Trials were carried out in the Shannon estuary, Ireland, to test the effects of continuous (CPs) and responsive pingers (RPs) on bottlenose dolphin behaviour. In controlled trials, active and control pingers were deployed on fixed moorings, with T-PODs—acoustic monitoring devices to detect cetacean activity. In a separate trial, pingers were deployed from a moving boat which actively located dolphin groups in the estuary, and dolphin behaviour was recorded. In the static trials, overall detection rates of dolphin vocalizations on the T-POD were significantly lower in the presence of active CPs, but this was not the case for RPs. Mean inter-click interval values were longer for click trains produced in the presence of inactive RPs than for active RPs, active or inactive CPs. In boat-based trials, both active CPs and RPs appeared to affect bottlenose dolphin behaviour, whereby dolphins immediately left the area at speed and in a highly directional manner, involving frequent leaps.

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