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Acoustic monitoring of the temporal and spatial occurrence of odontocetes off Blyth, Northumberland

Lookup NU author(s): Andrew Temple, Dr Per Berggren

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This is the authors' accepted manuscript of a report that has been published in its final definitive form by School of Marine Science and Technology (MAST), Newcastle University, 2015.

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Abstract

This project investigated the temporal occurrence of delphinids (white-beaked dolphin Lagenorhynchus albirostris and common bottlenose dolphin Tursiops truncatus) and harbour porpoise Phocoena phocoena using cetacean click detectors (C-PODs) at seven locations off Blyth, Northumberland between 18 June and 27 September 2015. The locations included three areas of interest and four control sites. The areas of interest were West (shallow water) and East (deeper water) of the Orec/Catapult testing platform and Cambois Bay. The four control sites were situated to the North and South of the testing platform locations. The CPODs provided continuous monitoring over 102 days (2448 hours) across six of the locations and 82 days (1968 hours) at the Cambois Bay location.Variation in the relative occurrence of delphinids (mixed species) and porpoise by location and temporal variables (time of day and month) were investigated using detection positive minutes of click trains. Further, location and temporal variation in relative foraging activity was also investigated using buzz click trains as a proxy for foraging activity.There were significant differences in relative delphinid occurrence among sites with a relative higher occurrence at the Cambois Bay location than any other location supporting anecdotal reports that this may be a site of relatively high occurrence of delphinids in the area. Further, higher relative delphinid occurrence was recorded at the two test locations by the Orec/Catapult testing platform than the corresponding control sites to the North and South. Delphinid relative occurrence across all sites decreased during hours of daylight and became near non-existent around midday. Further, dolphin relative occurrence was, in general, higher in July and August compared to June and September. Relative delphinid foraging activity was highest at Cambois Bay and at the East test site compared to the control sites. The latter was unexpected and suggests that foraging activity represents a greater proportion of delphinid behavioural budget in this location. This indicates that the East test site is likely an important foraging area. The relative occurrence appeared to be lowest at the three areas of interest between 11:00 and 15:00 and foraging behaviours were consistently low between 07:00 and 21:00.Differences in the overall relative occurrence and foraging activity of porpoises were also found among study locations. Highest levels of relative occurrence were observed in the East test site and the North inshore control site. Variations in relative porpoise occurrence with time of day were minimal, however at the two test locations by the Orec/Catapult testing platform there may be evidence for a small peak in relative occurrence between 04:00 and 09:00. Further, there was a general increase in porpoise relative occurrence in the months of July, August and September compared to that of June. Relative foraging activity followed a very similar pattern among locations, indicating the proportion of porpoise behavioural budget for foraging varies little among locations. Foraging behaviours were relative consistent during all hours of the day, with a potential minor reduction during hours of daylight. In conclusion, delphinid relative occurrence was lower in June and September compared to July and August, delphinid occurrence and foraging activity decreased during hours of daylight across all sites and the relative occurrence was higher at the two test locations and at Cambois Bay than the corresponding control sites. Harbour porpoise relative occurrence was lower in June compared to all other months, porpoise occurrence and foraging activity were relative consistent during all hours of the day, and the relative occurrence and foraging showed no clear pattern between control and test sites. A future monitoring programme using additional acoustic recorders covering a larger area throughout the year would have a greater power to detect potential changes in delphinid and porpoise spatial and temporal occurrence and foraging activity. The study provides important information on the spatial and temporal relative occurrence and foraging activity of delphinids and harbour porpoise off Blyth Northumberland that may facilitate for conservation of the species concerned and for management of anthropogenic activities that may affect the species.


Publication metadata

Author(s): Temple A, Berggren P

Publication type: Report

Publication status: Unpublished

Series Title:

Year: 2015

Pages: 16

Print publication date: 01/05/2016

Report Number:

Institution: School of Marine Science and Technology (MAST), Newcastle University

Notes: Report to EDF Energy


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