[MARMAM] New publication: Environmental status of the short-beaked common dolphin

[Camilo Saavedra Penas]

Dear All,

We are pleased to announce a new publication in the Special Issue 
"Multidisciplinary integrated surveys" of the Journal "Progress in 
Oceanography"

Title: "Assessing the environmental status of the short-beaked common 
dolphin (/Delphinus delphis/) in North-western Spanish waters using 
abundance trends and safe removal limits"
By: Camilo Saavedra, Tim Gerrodette, Maite Louzao, Julio Valeiras, 
Salvador García, Santiago Cerviño, Graham J.Pierce and M. Begoña Santos

The following link provides 50 days' free access to the paper: 
https://authors.elsevier.com/a/1XXhXI7ECcM1a

Highlights
Multidisciplinary surveys are shown to be useful platforms for 
monitoring cetaceans.
A positive trend in regional abundance of common dolphins was detected.
Safe bycatch limits have been calculated for common dolphins in the 
study region.
The Good Environmental Status of the common dolphin has been evaluated.
The abundance indicates a good status but the bycatch is difficult to 
interpret.

Abstract
Monitoring and assessment of the status of marine mammal populations is 
a requirement of the European Marine Strategy Framework Directive 
(MSFD). Due to the difficulty of collecting data in the marine 
environment and because many populations of these highly mobile species 
inhabit waters of several Member States, monitoring of marine mammals is 
particularly challenging. In the present work we have used a 10-year 
time-series of data collected from multidisciplinary research surveys to 
estimate common dolphin (/Delphinus delphis/) abundance and trends in 
continental shelf waters of the northwest Spanish sub-region. We argue 
that this approach provides a valuable addition to large-scale dedicated 
surveys, offering a shorter interval between surveys and hence offering 
the possibility to track abundance changes at a regional scale. Trends 
in the number of dolphins present in the study area over the last 
10 years show a mean increase of about 9.6% per year, which results in 
an evaluation of Good Environmental Status for the species in the area 
using the abundance indicator adopted in the framework of the MSFD. Data 
obtained from dedicated dual-platform surveys have been used to correct 
the detection bias in our data collected using single-platforms 
(attraction toward the observation platform and animals missed on the 
track-line), to obtain absolute abundance estimates for calculating 
bycatch limits. The average abundance over the study period was 12,831 
dolphins [CI 95%; 9025, 18,242] calculated with the conventional 
distance sampling methodology, 4747 [3307, 6816] corrected for 
attraction and missed animals on the track-line, and 22,510 [15,776, 
32,120] corrected only for missed animals on the track-line. The 
estimated safe bycatch limit for this area calculated from these 
abundance values were 218 [153, 310], 81 [56, 115] and 383 [268, 546] 
per year, respectively. Comparing these figures with estimates based on 
different sources, the percentage of dolphins that die in this study 
area is higher than the maximum limit allowable under the OSPAR criteria 
for population mortality adopted as an indicator for the MSFD.

Best regards,

Camilo Saavedra, Ph.D.
Instituto Español de Oceanografía http://www.ieo.es/
e-mail: camilo.saavedra at ieo.es




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