UNIVERSIDADE DOS AÇORES
DEPARTAMENTO DE OCEANOGRAFIA E PESCAS
“Temporal variability of cetaceans in the Azores and its
relation with oceanographic features as derived by satellite
imagery”
A Thesis Presented to the Faculty of the Department of Oceanography and Fisheries at the University of the Azores in Partial Fulfilment of the Requirements for the
Degree of Master of Integrated Studies of the Oceans
Marilia Pereira Olio
Horta
-2016-© Marilia Pereira Olio All Rights Reserved
UNIVERSIDADE DOS AÇORES
DEPARTAMENTO DE OCEANOGRAFIA E PESCAS
“Temporal variability of cetaceans in the Azores and its
relation with oceanographic features as derived by satellite
imagery”
A Thesis Presented to the Faculty of the Department of Oceanography and Fisheries at the University of the Azores in Partial Fulfilment of the Requirements for the
Degree of Master of Integrated Studies of the Oceans
Marilia Pereira Olio
Advisor
Ana Maria de Pinho Ferreira da Silva Fernandes Martins
Co-advisor
Paola Tepsich
Horta
-2016-PUBLICATIONS
Results of this study were already presented in two international conferences:
Olio M., Santos R.P, Tepsich P. and Martins A. (2015). A three year study of humpback whale (Megaptera novaeangliae) occurrence in Faial-Pico islands of the Azores and its relation to satellite-derived surface biophysical products. 29th Annual Conference of the European Cetacean Society. Malta: European Cetacean Society.
Olio M., Santos R.P, Tepsich P. and Martins A. (2016). A Three Year Study of Four Species of Baleen Whales Occurrence in Faial-Pico Islands of the Azores and its Relation to Satellite-derived Surface Biophysical Products. 2016 Ocean Sciences
Meeting, USA: American Geophysical Union.
One paper is under preparation for publication in international peer reviewed scientific journal:
Olio M., Santos R.P, Tepsich P. and Martins A. (2017). Temporal variability of cetaceans in the Azores and its relation with oceanographic features. In Prep.
Temporal variability of cetaceans in the Azores and its relation with oceanographic features as derived by satellite imagery i Temporal variability of cetaceans in the Azores and its relation with oceanographic features as derived by satellite imagery i ABSTRACT
The Archipelago of the Azores (Portugal) is composed of nine volcanic islands in the northeast Atlantic Ocean and it holds a high diversity of cetaceans, with 28 species documented. This is the first study in the Azores that assesses the utility of whale watching data for scientific studies on cetacean distribution, and that relates their occurrence and variability with 1 km resolution MODIS/AQUA near-surface chlorophyll a (Chla) and Sea Surface Temperature (SST) data obtained from NASA Ocean Color website. In this study, five years of field data (2010-2014) were used to evaluate blue, fin, sei and humpback whales presence. Three temporal scales (four years, yearly, and monthly) were considered. Given that effort was not consistent throughout, then encounter rates (ER=sightings.effort-1) were used as standardized measures for presence
temporal comparisons. Daily satellite Chla concentrations and SST values were statistically processed such as to obtain monthly, seasonal, annual averages, trends and anomalies for the period 2010 to 2014 for the Azores region. Baleen whales presence was related with the oceanographic data to infer possible causes for whales inter-annual variability Main results showed that the presence of the four baleen whale species in the Azores varied among the years. Intra-seasonal differences were found for presence rates and these varied with the species. The Bm presence was observed during the springtime suggesting that they use the Azores for foraging activity during these months while they are in their migration journey to north and that the variation of Chla and the initiation of the bloom could determine their time in the area. Similar results were found for Bp but their association with Chla and the timing of the bloom is later than the Bm. Since Bp is more opportunistic and has a varied diet, this happened since their prey could be in another level of the food chain. The peak for Bb varied in the spring and summer months and these differences could be explained by the assumption previously made by other authors, that maybe the Azores is visited by two different stocks of Bb, one during the migration in spring time and the second during late summer and autumn. Furthermore, the Chla concentration could be a biological parameter associated with the peak of Bb only for one stock. Lastly, the presence peaks of Mn were observed mostly during the spring and the number of sightings per month doubled in 2014 and 2015, suggesting that Mn could have foraged during these months while they were in their migration journey to north. Sea surface temperature and Chla concentration overall averages, adjusted averages (trends) and anomalies, as well as, calculations of the timing of the blooms show that the seasonal cycle is strong at these latitudes and inter-annual variability may explain differences in whales presence over the years. By removing the seasonal cycle, SST is very conservative over the years, and its trend reveals slight increase with time. Regarding Chla concentrations, spring blooms are not always observed in the region, but 2010 and 2014 reveal the strongest ones, coincident also with an overall increase in baleen whales observation, particularly for 2014. The use of platforms of opportunity may provide scientists a means of collecting data on a wide range of marine fauna when research funding is limited. Nevertheless, and in face with all the limitations found in the cetacean data, this study presents new suggestions for sampling protocols improvement such data from whale watching in MONICET might yield better possibilities for scientific purposes in the Azores.
Temporal variability of cetaceans in the Azores and its relation with oceanographic features as derived by satellite imagery ii Temporal variability of cetaceans in the Azores and its relation with oceanographic features as derived by satellite imagery ii RESUMO
O Arquipélago dos Açores (Portugal) é composto por nove ilhas vulcânicas no nordeste Oceano Atlântico e detém uma elevada diversidade de cetáceos, com 28 espécies documentadas. Este é o primeiro estudo nos Açores, que avalia a utilidade de dados do turismo de observação de baleias para estudos científicos sobre a distribuição dos cetáceos, e que relaciona a sua ocorrência e variabilidade com imagens MODIS/AQUA de clorofila a (Chla) e temperatura à superfície (SST) com 1 km de resolução obtidas através do site da NASA Ocean Color. Neste estudo, cinco anos de dados de campo (2010-2014) foram utilizados para avaliar a presença das baleias azul, comum, sardinheira e bossas. Fora consideradas três escalas temporais (quatro anos em conjunto, anuais e mensais). Dado que o esforço não foi consistente ao longo dos anos, as taxas de avistamento (Encounter rate, ER=avistamentos.esforço-1) foram utilizadas como medidas
padronizadas para comparações temporais de presença. Imagens diárias de Chla e SST foram processadas estatisticamente, obtendo-se médias mensais, sazonais, anuais, tendências e anomalias para o período de 2010 a 2014 para a região dos Açores e relacionados com a variabilidade local de quatro espécies de baleias de barbas para tentar explicar as diferenças registadas ao longo dos anos. Os principais resultados mostraram que a presença das quatro espécies de baleias de barbas nos Açores variou entre os anos. Diferenças intra-sazonais foram encontradas para as taxas de presença e estas variaram de acordo com a espécie. A presença de Bm foi observada durante a primavera sugerindo que estas baleias usam os Açores como área de alimentação durante estes meses enquanto estão na sua rota de migração para norte e que, a variação de Chla e o início do crescimento do fitoplâncton são bons indicadores do tempo efectivo destas na região. Resultados semelhantes foram encontrados para a BP, mas a sua associação com Chla e o momento do crescimento do fitoplâncton é posterior à Bm Sendo a Bp mais oportunista e tendo uma dieta mais variada, as suas presas podem estar a níveis diferentes cadeia alimentar. O pico de Bb variou nos meses de primavera e verão e estas diferenças podem ser explicadas pela suposição, já referida por outros autores, de que os Açores provavelmente são visitados por duas populações diferentes de Bb, uma durante a fase de migração na primavera e a segunda durante o final do verão e no outono. Assim sendo, a concentração de Chla seria um parâmetro biológico associado com o pico de Bb apenas para uma das populações. Por último, os picos de presença de Mn foram observados principalmente durante a primavera e o número de meses dos avistamentos duplicou em 2014 e 2015, sugerindo que Mn poderia utilizar os Açores como área de alimentação durante estes meses, durante o seu caminho de migração para norte. A temperatura da superfície do mar, a concentração de Chla e o início do crescimento do fitoplâncton, aqui ilustrados como médias gerais, médias ajustadas (tendências) e anomalias, suportam a hipótese de que o ciclo sazonal e a variabilidade inter-anual são bem demarcados nesta região podendo explicar as diferenças observadas na presença das baleias ao longo os anos. Ao remover o ciclo sazonal, SST é muito conservador ao longo dos anos, com uma ligeira tendência de aumento com o tempo. Com relação à Chla, nem todos os anos apresentam floração de primavera, mas 2010 e 2014 revelam os picos maiores de Chla, coincidindo também com um aumento global de observação das baleias, particularmente para 2014. O uso de plataformas de oportunidade pode dar aos cientistas um meio de recolha de dados sobre uma ampla gama de fauna marinha quando o financiamento da investigação é limitada. No entanto, face às limitações encontradas nos dados de cetáceos, este estudo apresenta novas sugestões de introdução nos protocolos de amostragem por forma a que os dados MONICET possam produzir dados detalhados para fins científicos. Palavras-chave: Baleias de barbas; Açores; Temperatura superficial; Clorofila.
Temporal variability of cetaceans in the Azores and its relation with oceanographic features as derived by satellite imagery iii Temporal variability of cetaceans in the Azores and its relation with oceanographic features as derived by satellite imagery iii ACKNOWLEDGMENTS
This thesis is a result of three years of my life spent in one of the most beautiful places I have ever been and where it provided so much knowledge about cetaceans and about myself.
I am very grateful and thankful to both my supervisor, Prof. Dr. Ana Martins and co-supervisor Dr. Paola Tepsich, for all their patience and time taken, and for never letting me give up of this work until the end. With you, I can say with no doubts that your teachings made me feel a much better researcher and independent professional person.
I thank Pedro Filipe, my friend and boss in HortaCetáceos, for the opportunity of realizing my dream of living in the Azores, by allowing me to work part-time in his enterprise and in this way, by helping to support my studies at the University. Last but not least, I am very grateful for making my job so fun; allowing me to be at sea with the whales and dolphins every time this was possible.
I am also grateful to the University of the Azores (Portugal) and to CIMA Foundation (Italy) for supporting this project, and for providing financial support for my stay two months at CIMA Foundation through an ERASMUS placement scholarship.
I am very grateful to project MONICET, and in special to Marc Fernandez, and all the other whale watching companies (Picos de Aventura, Terra Azul, and Ocean Emotion) and their crew for allowing me to access their data. Thanks are also equally important to HortaCetáceos crew and Carla, and also to Rui Santos from Espaço Talassa for making their data available for my study.
I would like to acknowledge NASA for the use of their satellite oceanographic Level2 dataset and the HAZO system developed at the Oceanography Section at DOP/UAz, through informatics engineer Miguel Figueiredo, for access to post-processed satellite data.
I would also like to acknowledge my professors Dr. Gui Menezes and Dr. Mário Pinho.
Temporal variability of cetaceans in the Azores and its relation with oceanographic features as derived by satellite imagery iv Temporal variability of cetaceans in the Azores and its relation with oceanographic features as derived by satellite imagery i her support, love and for never stop believing in me. To my friends Marito PL1, Mi PL2, Li, Lelê, and Alê, who were not physically with me but showed me that the distance is not an issue for a friendship. I am also very grateful to my friends Rita meninas, Clare, Carol, Ana bifana, Gonçalo, Susana, Anita and Marco, who accompanied me along these years. To my friends Ká, Xuxuzinho and Bia who closely followed this long journey. To Sónia Pó who in recent months has been essential to give me the strength to complete this phase of my life. To my friends Massi, Isa and Frazer who made my time spent in Italy very special. Last but no least, I thank all the friends who are not mentioned here, but that are no less important by being very essential in my life over the years.
I am also very thankful to the staff members at the Department of Oceanography and Fisheries and at the International Relations Office at the University of the Azores (Portugal) for all the logistics help during this process.
Lastly, I would like to leave a grateful note to the members of the jury present in the oral defense of my thesis, for abdicating their precious time to read the thesis manuscript and to listen and watch my oral presentation. This effort is greatly appreciated.
Temporal variability of cetaceans in the Azores and its relation with oceanographic features as derived by satellite imagery v Temporal variability of cetaceans in the Azores and its relation with oceanographic features as derived by satellite imagery INDEX Abstract………...i Resumo………...………...ii Acknowledgments……….iii Index………...v List of Tables………...vii List of Figures………....………...ix Introduction………1 Background………4 1. Blue whales………....4 2. Fin whales………...10 3. Sei whales……….……...15 4. Humpback whales……….……...19 5. The Azores………..……….23 6. Oceanographic Features………...24
7. Whale Watching and Cetaceans in the Azores………25
Methodology………....28 1. Study Area………....28 2. Field Work……...28 3. Data Processing...29 4. Data Analysis...34 Results………...39
1. Temporal Variability of Presence...39
2. Oceanographic Data...49
Temporal variability of cetaceans in the Azores and its relation with oceanographic features as derived by satellite imagery vi Temporal variability of cetaceans in the Azores and its relation with oceanographic features as derived by satellite imagery i
1. Environmental Analysis...67
2. Baleen Whales Presence in the Azores...78
3. Problems Encountered with Cetaceans Database...82
Conclusions...85
Temporal variability of cetaceans in the Azores and its relation with oceanographic features as derived by satellite imagery vii Temporal variability of cetaceans in the Azores and its relation with oceanographic features as derived by satellite imagery ii LIST OF TABLES
Table I. Total number of days and trips per month and per year. ... 30 Table II. Number of days and trips per month and year where effort data and baleen whale sightings were available. ... 30 Table III. Summarized information of the years of available data; species identified; and number of companies’ vessels. The later, also indicate in brackets the number of vessels that collected data for each company. ... 31 Table IV. Total number of sightings over the study period in the Azores. ... 33 Table V. Annual variation of the presence of the four baleen whale species all together and for each species separately. Blue whale is designated by Bm, fin whale by Bp, sei whale by Bb, and humpback whale by Mn. Statistical Kruskal-Wallis test (λ2 and p-value) and respective Dunn’s multiple comparisons test (MCT) for a 95% confidence interval (CI). ... 40 Table VI. Yearly variation of the baleen whale species presence for each month sampled. Statistical Kruskal-Wallis test (λ2 and p-value) and respective Dunn’s multiple comparisons test (MCT) for a 95% confidence interval (CI). ... 42 Table VII. Yearly variation of the presence for each species of baleen whales separately for each month sampled. Blue whale is designated by Bm, fin whale by Bp, sei whale by Bb, and humpback whale by Mn. Statistical Kruskal-Wallis test (λ2 and p-value) and respective Dunn’s multiple comparisons test (MCT) for a 95% confidence interval (CI). ... 43 Table VIII. Monthly variation of the presence of the four baleen whale species all together and for each species separately. Blue whale is designated by Bm, fin whale by Bp, sei whale by Bb, and humpback whale by Mn. Statistical Kruskal-Wallis test (λ2 and p-value) and respective Dunn’s multiple comparisons test (MCT) for a 95% confidence interval (CI). ... 45
Temporal variability of cetaceans in the Azores and its relation with oceanographic features as derived by satellite imagery viii Temporal variability of cetaceans in the Azores and its relation with oceanographic features as derived by satellite imagery iii Table IX. Monthly variation of the baleen whale species presence for each year sampled. Statistical Kruskal-Wallis test (λ2 and p-value) and respective Dunn’s multiple comparisons test (MCT) for a 95% confidence interval (CI). ... 48 Table X. Monthly variation of each species of whale presence for each year sampled. Statistical Kruskal-Wallis test and respective Dunn’s multiple comparisons test (MCT) for a 95% CI. ... 49 Table XI. Application of the Siegel et al. (2002) method to infer phytoplankton growth phases for the periods 2010 to 2014 in the Azores. The table provides information on: 1) the chlorophyll a (Chla) concentration that represents the initiation of the phytoplankton growth (5% above the median), its respective month, and sea surface temperature (SST) average; 2) chlorophyll a (Chla) maximum concentration, its respective month, and sea surface temperature (SST) average; and 3) the duration of the initiation of the bloom up to its maximum peak (in months). ... 57 Table XII. Comparison of the timing of the onset bloom (initiation of the phytoplankton growth), the peak of the chlorophyll a (Chla) concentration, the end of the bloom, and the duration of the bloom and their respective standard deviation (SD)
during the years 2004 to 2007 in the Azores by applying Visser et al. (2011) method
on 1 km (left) and 4 km (right) MODIS/AQUA Chla near-surface concentrations.... 74
Table XIII. Comparison between the Siegel et al. (2002) and the Visser et al. (2011) methods to calculate phytoplankton initiation and growth for the years 2004 to 2008 in the Azores. Table indicates the chlorophyll a (Chla) maximum concentration and its respective week of the year; comparing the timing of the initiation of the phytoplankton growth (5% above the median or onset bloom), their respective week of the year, and the duration of the bloom. ... 75 Table XIV. Comparison between the Siegel et al. (2002) and the Visser et al. (2011) methods to calculate phytoplankton initiation and growth for the years 2010 to 2014 in the Azores. Table indicates the chlorophyll a (Chla) maximum concentration and its respective week of the year; comparing the timing of the initiation of the phytoplankton growth (5% above the median or onset bloom), their respective week of the year, and the duration of the bloom. ... 75
Temporal variability of cetaceans in the Azores and its relation with oceanographic features as derived by satellite imagery ix Temporal variability of cetaceans in the Azores and its relation with oceanographic features as derived by satellite imagery i LIST OF FIGURES
Figure 1. Blue whale (adapted illustration from ©Frédérique Lucas). ... 5 Figure 2. Blue whale characteristic dive sequence (adapted illustration from Sandra Doyle, Natural History Museum of New York). ... 5 Figure 3. Blue whale distribution (yellow) map (IUCN Red List)... 8 Figure 4. Fin whale (adapted illustration from ©Frédérique Lucas). ... 11 Figure 5. Fin whale characteristic sequence dive (adapted illustration from Sandra Doyle, Natural History Museum of New York). ... 11 Figure 6. Fin whale distribution (yellow) map (IUCN Red List). ... 14 Figure 7. Sei whale (adapted illustration from ©Frédérique Lucas). ... 15 Figure 8. Sei whale characteristic sequence dive (adapted illustration from Sandra Doyle, Natural History Museum of New York). ... 16 Figure 9. Sei whale distribution (yellow) map (IUCN Red List). ... 18 Figure 10. Humpback whale (adapted illustration from ©Frédérique Lucas). ... 19 Figure 11. Humpback whale characteristic sequence dive (adapted illustration from Sandra Doyle, Natural History Museum of New York). ... 20 Figure 12. Humpback whale distribution (yellow) map (IUCN Red List). ... 21 Figure 13. Study area with indication of the four main islands where whale watching occurs. ... 28 Figure 14. General scheme of the temporal analyses performed in this study with illustration of null hypotheses. ... 35 Figure 15. Annual encounter rates (ER) averages for the four baleen whale species during the years 2011 to 2015 in the Azores. Barplot diagram representing the annual ER averages and standard deviations (SE) (left); and Annual ER averages (black line) and 5-year total ER average (dashed black line) (right). ... 39
Temporal variability of cetaceans in the Azores and its relation with oceanographic features as derived by satellite imagery x Temporal variability of cetaceans in the Azores and its relation with oceanographic features as derived by satellite imagery Figure 16. Annual encounter rates (ER) averages for blue whale (Bm) during the years 2011 to 2015 in the Azores. Barplot diagram representing the annual ER averages and standard deviations (SE) (left); and Annual ER averages (black line) and 5-year total ER average (dashed black line) (right). ... 40 Figure 17. Annual encounter rates (ER) averages for fin whale (Bp) during the years 2011 to 2015 in the Azores. Barplot diagram representing the annual ER averages and standard deviations (SE) (left); and Annual ER averages (black line) and 5-year total ER average (dashed black line) (right). ... 41 Figure 18. Annual encounter rates (ER) averages for sei whale (Bb) during the years 2011 to 2015 in the Azores. Barplot diagram representing the annual ER averages and standard deviations (SE) (left); and Annual ER averages (black line) and 5-year total ER average (dashed black line) (right). ... 41 Figure 19. Annual encounter rates (ER) averages for humpback whale (Mn) during the years 2011 to 2015 in the Azores. Barplot diagram representing the annual ER averages and standard deviations (SE) (left); and Annual ER averages (black line) and 5-year total ER average (dashed black line) (right). ... 42 Figure 20. Monthly encounter rates (ER) averages for the baleen whale species during the years 2011 to 2015 in the Azores. ... 44 Figure 21. Monthly encounter rates (ER) averages for blue whale (Bm) during the years 2011 to 2015 in the Azores. ... 46 Figure 22. Monthly encounter rates (ER) averages for fin whale (Bp) during the years 2011 to 2015 in the Azores. ... 46 Figure 23. Monthly encounter rates (ER) averages for sei whale (Bb) during the years 2011 to 2015 in the Azores. ... 47 Figure 24. Monthly encounter rates (ER) averages for humpback whale (Mn) during the years 2011 to 2015 in the Azores. ... 48 Figure 25. MODIS-derived sea surface temperature (SST) monthly average (black line) and adjusted average (dashed grey line) variation during the years 2010 to 2014
Temporal variability of cetaceans in the Azores and its relation with oceanographic features as derived by satellite imagery xi Temporal variability of cetaceans in the Azores and its relation with oceanographic features as derived by satellite imagery i in the Azores. Maximum and minimum SST values for each year are indicated in the graphic. ... 50 Figure 26. MODIS-derived sea surface temperature (SST) monthly variation during the years 2010 to 2014 in the Azores: a) average variation; b) adjusted average variation. ... 51 Figure 27. MODIS-derived sea surface temperature (SST) seasonal average (black line) and adjusted average (dashed grey line) variation during the years 2010 to 2014 in the Azores. ... 52 Figure 28. MODIS-derived sea surface temperature (SST) seasonal variation during the years 2010 to 2014 in the Azores: a) average variation; b) adjusted average variation. ... 53 Figure 29. MODIS-derived sea surface temperature (SST) annual average (black line) and adjusted average (dashed grey line) variation during the years 2010 to 2014 in the Azores. Maximum and minimum SST values for each year are indicated in the graphic. The regression equation and the coefficient of determination (R2) are also provided. ... 54 Figure 30. MODIS-derived chlorophyll a (Chla) monthly average variation (red line), adjusted average variation (dashed black line), median (blue line), and initiation of the phytoplankton growth (vertical green line) during the years 2010 to 2014 in the Azores. Maximum and minimum Chla values for each year are indicated in the graphic: a) to e) represent the years 2010 to 2014, respectively. ... 55 Figure 31. MODIS-derived chlorophyll a (Chla) monthly variation during the years 2010 to 2014 in the Azores: a) average variation; b) adjusted average variation. ... 56 Figure 32. MODIS-derived chlorophyll a (Chla) seasonal average variation (red line), adjusted average variation (dashed black line), and median (blue line) during the years 2010 to 2014 in the Azores. ... 59 Figure 33. MODIS-derived chlorophyll a (Chla) seasonal variation during the years 2010 to 2014 in the Azores: a) average variation; b) adjusted average variation. ... 60
Temporal variability of cetaceans in the Azores and its relation with oceanographic features as derived by satellite imagery xii Temporal variability of cetaceans in the Azores and its relation with oceanographic features as derived by satellite imagery ii Figure 34. MODIS-derived chlorophyll a (Chla) annual average variation (red line), adjusted average variation (dashed black line), and median (blue line) during the years 2010 to 2014 in the Azores. Maximum and minimum Chla values for each year are indicated in the graphic. ... 60 Figure 35. Histograms of MODIS-derived seasonal average variation during the years 2010 to 2014 in the Azores: a) sea surface temperature (SST) average; b) chlorophyll
a (Chla) average. ... 61 Figure 36. MODIS-derived sea surface temperature (SST) (black line) and chlorophyll a (Chla) (dashed grey line) monthly average anomalies for the years 2010 to 2014 in the Azores. ... 62 Figure 37. MODIS-derived sea surface temperature (SST) (black line) and chlorophyll a (Chla) (dashed grey line) monthly adjusted average anomalies for the years 2010 to 2014 in the Azores. ... 63 Figure 38. MODIS-derived sea surface temperature (SST) (black line) and chlorophyll a (Chla) (dashed grey line) seasonal average anomalies for the years 2010 to 2014 in the Azores. ... 64 Figure 39. MODIS-derived sea surface temperature (SST) (black line) and chlorophyll a (Chla) (dashed grey line) seasonal adjusted average anomalies for the years 2010 to 2014 in the Azores. ... 64 Figure 40. MODIS-derived sea surface temperature (SST) (black line) and chlorophyll a (Chla) (dashed grey line) annual average anomalies for the years 2010 to 2014 in the Azores. ... 65 Figure 41. MODIS-derived sea surface temperature (SST) (black line) and chlorophyll a (Chla) (dashed grey line) annual adjusted average anomalies for the years 2010 to 2014 in the Azores. ... 66
Temporal variability of cetaceans in the Azores and its relation with oceanographic features as derived by satellite imagery 1 Temporal variability of cetaceans in the Azores and its relation with oceanographic features as derived by satellite imagery 1 INTRODUCTION
Cetacean distribution and relative abundance in offshore waters of the North Atlantic remain largely unknown. Previous research studies, particularly those related with the North Atlantic Sighting Surveys (NASS 1985-2001), allowed some new information regarding cetacean distribution and population size. However, none of these surveys covered the mid-Atlantic waters (Silva et al., 2014). The first systematic survey information on cetacean distribution and density in this region was realized during the Mid-Atlantic Ridge Ecology Program (MAR-ECO) in June-July 2004 (Waring et al., 2008).
The Archipelago of the Azores (Portugal) is composed of nine volcanic islands and several small islets in the northeast Atlantic Ocean about 1,360 km (850 mi) west of continental Portugal. The islands form three main groups: Flores and Corvo, to the west; Graciosa, Terceira, São Jorge, Pico, and Faial in the centre; and São Miguel, Santa Maria, and the Formigas Reef to the east. They extend along a west-northwest to east-southeast orientation (between 36.5°– 40° North latitudes and 24.5°– 31.5° West longitudes) in an area approximately 600 km (373 mi) wide.
The marine environment of the Azores Archipelago and its surrounding Economic Exclusion Zone (EEZ), of more than 1 million km2, holds considerable marine biodiversity, conservation, geostrategic and economic interests (e.g. Santos et al., 1995; Bashmachnikov et al., 2009; Ciancia et al., 2016). The area holds a high diversity of cetaceans, with 28 species documented (reviewed in Prieto and Silva 2010; Silva et al., 2012). The first assessment of the spatial and temporal distribution patterns of cetaceans around the Azores has been provided by Silva (2014), who used data collected during sighting surveys from land-based observations to provide the first assessment of the spatial and temporal distribution patterns of cetaceans around the Azores.
The use of platforms of opportunity, such as whale watching vessels (Magalhães et al., 2002; Croll et al., 2005; Ingram et al., 2007; Esteban et al., 2013; Randage et al., 2014; Tepsich, 2015; Vinding et al., 2015), seismic survey vessels (Fernandes et al., 2007; Muir et al., 2015), commercial ships (Viddi et al., 2010; Correia et al., 2015) or ferries (Morgado, 2013; Aïssi et al., 2015; Cominelli et al., 2015; Arcangeli et al.,
Temporal variability of cetaceans in the Azores and its relation with oceanographic features as derived by satellite imagery 2 Temporal variability of cetaceans in the Azores and its relation with oceanographic features as derived by satellite imagery 2 2016) is currently recognized as a valuable alternative to dedicate research effort, that is usually expensive and time consuming. Data collected from these platforms have been widely used to provide alternative sources of data on cetaceans, especially in developing countries, and information on spatial distribution, temporal patterns in abundance, and behaviour have been acquired (Ingram et al., 2007; Esteban et al., 2013; Morgado, 2013; Cominelli et al., 2015; Correia et al., 2015; Vinding et al., 2015). However, such data need to be interpreted with caution, especially given spatial or temporal differences in effort or variation in observer ability to correctly identify species (Tepsich, 2015; Vinding et al., 2015).
In the Azores archipelago, whale watching has been occupying an increasingly important role at a socio-economical level and it is growing rapidly (Magalhães et al., 2002). In 1989 there was some experimental activity with some foreigner (English and French) local entrepreneurs, but it was in 1993 that this activity was fully initiated) (Hoyt, 1992). In 2011, within the framework of project MONICET, funded by the Regional Government of the Azores, a first whale watching database platform was constructed. Since then, MONICET has been collecting cetaceans’ observation of several whale watching companies in Portugal, providing free data for scientific studies and public information. However, to the best our knowledge, with an exception a graduate thesis (Silva, 2013), this database has never been used for scientific publication.
Increased interest in understanding the occurrence, distribution and behaviour patterns, of different cetacean species present in Azores waters resulted in a number of research programs and/or projects in the region in the past decade. These studies show strong seasonal and inter-annual cetacean variability in the region (Silva et al., 2014), others suggest physical/biological mechanisms responsible for this variability (e.g. frontal thermal structures (Silva, 2013; Prieto et al., 2016). However, most fail to relate inter-annual and seasonal variability in the region with biotic and abiotic anomalies or to compare episodic events with mesoscale dynamics.
In order to overcome this limitation, this study uses in situ data and MODIS/AQUA satellite derived imagery to provide new understanding of how the occurrence of cetacean might be linked/connected to large and/or mesoscale physical/biological processes in Azores waters.
Temporal variability of cetaceans in the Azores and its relation with oceanographic features as derived by satellite imagery 3 Temporal variability of cetaceans in the Azores and its relation with oceanographic features as derived by satellite imagery 3 Main objectives of this work are: first, to assess the utility of whale watching data for scientific studies on cetacean distribution; and second, to assess cetacean occurrence (i.e. presence/absence) in the Azores by relating its variability with satellite derived Ocean Colour (OC) and Sea Surface Temperature (SST) geophysical parameters. For this, five years of in situ cetacean data and satellite-derived imagery are used, comprising three seasons of the year (winter-spring-summer). To explain major cetacean occurrences, seasonal, annual, inter-annual and specific events anomalies are analysed to infer (local and regional) cetacean variability in the Azores.