Local movements and site-tenacity of minke whale in Iceland in relation to feeding and a northward distribution shift

ABSTRACT

Population dynamics, movement patterns and migratory routes of common minke whales (Balaenoptera acutorostrata) in the North Atlantic are not yet fully understood. Small-scale movements of minke whales within Skjálfandi Bay, Iceland, were analysed and discussed in relation to population dynamics in the North Atlantic. Local distribution and abundance of minke whales were investigated on both individual and population basis. Data were obtained through continuous sighting surveys from 2005 to 2018, conducted by trained volunteers using whale watching vessels as opportunistic research platforms. Variations in abundance might reflect a species distribution shift to higher latitudes. Competition for prey and the general movement of several species from different taxonomic groups support a potential range shift. For the first time, habitat use of minke whales in Skjálfandi Bay was revealed through spatial analysis, as well as small-scale site-tenacity, proven through modelling of distances between individual and random relocations. To improve the status of the declining minke whale population around Iceland we suggest recognition of separate minke whale management units using different areas. Additionally, we encourage the protection of different feeding grounds which will reduce local anthropogenic stressors and likely improve minke whales' coping with climate change and shifts in prey.

KEYWORDS:

• Feeding
• protected species
• marine mammals
• climate change

Acknowledgements

We thank the Húsavík Research Centre, the Húsavik Whale Museum, all students and volunteers for providing the long-term data catalogue. Thanks to North Sailing (https://www.northsailing.is/) and Gentle Giants for providing their vessels as a free research platform. Our gratitude is also expressed towards Jean-François Gerard for his help during the analysis. This work was financed by the Academic Scholarship for graduate students of the German DAAD (57380758–91687232) and the Erasmus+ Program of the European Union in collaboration with the IMBRSea Master program.

Disclosure statement

No potential conflict of interest was reported by the authors.

SUPPORTING INFORMATION

FIGURE S1. Body features used for individual identification: (A) Marks around the dorsal fin edge and (B) distinct dorsal fin shape and body scars. Originated from the photoidentification catalogue of the Húsavík Research Centre.

FIGURE S2. Number of trips over the years (A) and months (B) for sighting data collection.

FIGURE S3. Fish habitats for capelin (February–May), Atlantic cod (March & April) and small fish year-round.

FIGURE S4. Time between recaptures of the identified individual with average time of 496 days between recaptures (blue dotted line) and median time between recaptures of 250 days (red solid line).

TABLE SI. Likelihood ratio test for factor selection for the model: anova(model1,model2, test = ‘Chisq’). Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ‘ 1.

TABLE SII. Model selection after lowest AIC: glm(no∼factor + offset(log(hour)), data = data, family = Poisson()).

TABLE SIII. Goodness of fit test: with(model, cbind(res.deviance = deviance, df = df.residual,+ p = pchisq(deviance, df.residual, lower.tail = FALSE))).

TABLE SIV. Results of the Type III ANOVA with Satterthwaite's method on the linear mixed model with individual as random factor. Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ‘ 1.

TABLE SV. Individuals captured more than once.

Additional information

Funding

This work was supported by German Academic Exchange Service [Grant Number 57380758 - 91687232].