MONITORING THE ANOMALOUS PRESENCE OF BLUE SHARKS IN COASTAL WATERS OF GALICIA, SPAIN

Abstract

Blue shark Prionace glauca (L. 1758) (Carcharhinidae) is an oceanic–epipelagic and fringe littoral species worldwide distributed in temperate and tropical oceans. It is one of the most abundant, widespread, fecund and fastest growing sharks. Blue shark also is one of the most exploited shark species globally and in European waters.
The anomalous presence of numerous neonates and juveniles blue sharks in shallow inshore waters of Galicia, north-west Spain, was first observed in summer 2013 in the north of Galicia (Mejuto et al. 2014). This unusual phenomenon has been posteriorly confirmed by numerous observations along the Galician coasts in summer 2014 and 2015 (Bañón et al. 2016).
With the aim to obtain a continuous source data, these results, including a request for collaboration, have been divulgated through the traditional communication methods (press, radio and television) and new internet technologies and collaboration tools (facebook, twitter, blogs).
As results, during 2016 and 2017 a total of 65 new observations corresponding to 106 specimens have been reported in summer and autumn in Galician coasts. Changes in oceanographic conditions, high recruitment events or changes in the pupping area are the most possible causes of this unusual behavior. However, to reach solid conclusions an exhaustive follow-up of new observations are needed.
Citizen science is a crucial tool to register these observations. Common reported data are date, time, position, size or sex. Photographs and/or videos are also usually provided to confirm observation. All shark observations are continuously loaded to public online platforms via shiny apps.
This work is support by Ecoloxía Azul - Blue Ecology (Association of popular science and conservation).

Full text

References
Bañón, R., Maño, T., and Mucientes, G. 2016. Observations of newborn blue sharks Prionace glauca in shallow inshore waters of the north‐east Atlantic Ocean. Journal of Fish Biology,
89: 2167-2177.
Mejuto, J., García-Cortés, B., Ramos-Cartelle, A., and Abuin, E. 2014. Note on the observation of recruits of blue shark, Prionace glauca,in near coastal areas of Galicia (NW Spain)
during the summer of 2013. Collect. Vol. Sci. Pap. ICCAT, 70: 2452-2461.
@gmucientes @Fanequeiro @ecologiaazul @FisheriesIIM#coastalsharks #sharkscience #Galicia
MONITORING THE
ANOMALOUS PRESENCE
OF BLUE SHARKS IN
COASTAL WATERS OF
GALICIA, SPAIN
Background
Blue shark, Prionace glauca (L.1758), is an oceanic
epipelagic and fringe littoral species with a worldwide
distribution in temperate and tropical oceans. It is one of
the most abundant, fecund and fastest growing sharks.
The Blue shark is also one of the most exploited shark
species in global and European waters.
Question
Methods
What is the reason behind the anomalous occurrence of
juvenile blue sharks in Galician coastal waters, NW Spain,
during the last summers?
Results
Conclusions
With the aim of elucidating the main factors explaining the
anomalous presence of juveniles of P. glauca in coastal
waters off Galicia, we launched a monitoring program of
new records following a citizen science approach.
Reported data included date, position, size or sex.
Photographs and/or videos are usually provided to confirm
observation.
During 2016 and 2017 a total of 65 observations, totalizing 106 individuals, were
reported and data uploaded to apublic online platforms via shiny app.
Most records were registered during summer months (specially July), confirming
previous results (Bañón et al.2016).
Mean size of individuals was 70±26 cm total length.
The anomalous presence of numerous blue shark neonates and juveniles in
shallow inshore waters off Galicia was first observed in summer 2013 (Mejuto et al.
2014). This unusual phenomenon has been posteriorly confirmed with multiple
observations during 2014 and 2015 (Bañón et al. 2016) and this monitoring
program also confirm this phenomenon during 2016-2017.
Changes in oceanographic conditions, high recruitment events or changes in the
nursery area are the most probable causes of this unusual behavior. However, to
reach solid conclusions an exhaustive follow-up of new observations are needed.
Figure 3. Distribution of Blue shark records 2016-2017. Scan qR code to see the shiny app.
gonzalomucientes@gmail.com
https://ecologiaazul.com
Resumen
La presencia anómala de juveniles de tiburón azul,
Prionace glauca (L.1758), en aguas costeras poco
profundas de Galicia se observó por primera vez en el
verano de 2013. Este fenómeno inusual ha sido confirmado
posteriormente en los veranos de 2014 y 2015. El presente
trabajo amplía los registros de P. glauca en Galicia durante
el periodo 2016-2017 en 106 individuos.
G. Mucientes,
R. Bañón, A. Maño,
D. Villegas-Ríos and
A. Alonso-Fernández
Figure 2. Blue sharks in Galicia (Picture: Toño Maño, 2015). Scan qR code to see youtube video.
Figure 1. Frequency of blue shark records during 2016-2017
106
blue
sharks
July
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