Comparing Distribution of Harbour Porpoises (Phocoena phocoena) Derived from Satellite Telemetry and Passive Acoustic Monitoring.

Lonnie Mikkelsen,Rune Dietz,Line A Kyhn,Jonas Teilmann,Jakob Tougaard,Signe Sveegaard,Julia A K Carlström,Ida Carlén,Frank F Rigét,Jens C Koblitz

doi:10.1371/journal.pone.0158788

Lonnie Mikkelsen, Rune Dietz + Show 8 more

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https://doi.org/10.1371/journal.pone.0158788

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Abstract

Cetacean monitoring is essential in determining the status of a population. Different monitoring methods should reflect the real trends in abundance and patterns in distribution, and results should therefore ideally be independent of the selected method. Here, we compare two independent methods of describing harbour porpoise (Phocoena phocoena) relative distribution pattern in the western Baltic Sea. Satellite locations from 13 tagged harbour porpoises were used to build a Maximum Entropy (MaxEnt) model of suitable habitats. The data set was subsampled to one location every second day, which were sufficient to make reliable models over the summer (Jun-Aug) and autumn (Sep-Nov) seasons. The modelled results were compared to harbour porpoise acoustic activity obtained from 36 static acoustic monitoring stations (C-PODs) covering the same area. The C-POD data was expressed as the percentage of porpoise positive days/hours (the number of days/hours per day with porpoise detections) by season. The MaxEnt model and C-POD data showed a significant linear relationship with a strong decline in porpoise occurrence from west to east. This study shows that two very different methods provide comparable information on relative distribution patterns of harbour porpoises even in a low density area.

Highlights

Visual observations from plane or boat have long been the primary method to monitor cetaceans at sea [1]
This study demonstrates that the two independent methods presented here correlate in the sense that high habitat suitability, based on satellite positions, provides high acoustic activity patterns in a marine mammal species
The large scale findings of the species habitat model Maximum Entropy (MaxEnt) were reflected in the small scale findings of the acoustic data set

Summary

Introduction

Visual observations from plane or boat have long been the primary method to monitor cetaceans at sea [1]. As this still holds true for some species [2,3,4]), methods such as satellite telemetry [5,6]) and acoustic monitoring [7,8,9]) are increasingly being used to describe distribution patterns and relative occurrences. Satellite telemetry reveals the movement patterns of the tagged animals with spatial and temporal resolution depending on programming of the tags and use of satellite systems, e.g. GPS system within tens of meters and PLOS ONE | DOI:10.1371/journal.pone.0158788. Satellite telemetry reveals the movement patterns of the tagged animals with spatial and temporal resolution depending on programming of the tags and use of satellite systems, e.g. GPS system within tens of meters and PLOS ONE | DOI:10.1371/journal.pone.0158788 July 27, 2016

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