Injuries, Malformations, and Epidermal Conditions in Cetaceans of the Strait of Gibraltar

Injuries, Malformations, and Epidermal Conditions in Cetaceans of the Strait of Gibraltar

Injuries, Malformations, and Epidermal Conditions in Cetaceans of the Strait of Gibraltar

Wissenschaftliche Publikation von Jörn Selling und Katharina Heyer

Aquatic Mammals 2020, 46(2), 215-235

Die Publikation ist zum Download freigegeben:

Helena Herr, Patricia Burkhardt-Holm, Katharina Heyer, Ursula Siebert, and Jörn Selling

Abstract:

The Strait of Gibraltar is a heavily used marine area, with intense fishing operations and one of the busiest shipping lanes worldwide. Concurrently, the Strait of Gibraltar is home to eight regularly occurring species of cetaceans. Thus, the potential for conflict between man and cetaceans is high. Injuries and external anomalies may serve as indicators for anthropogenic impacts and exposure to human activities. To explore potential impacts to cetacean populations inhabiting the Strait of Gibraltar, we analysed photographs taken opportunistically during whale-watching operations from 2001 to 2015. Externally visible conspicuous features and anomalies were detected in all of the eight regularly occurring cetacean species: long beaked common dolphin (Delphinus delphis), striped dolphin (Stenella coeruleoalba), common bottlenose dolphin (Tursiops truncatus), long-finned pilot whale (Globicephala melas), killer whale (Orcinus orca), sperm whale (Physeter macrocephalus), fin whale (Balaenoptera physalus), and minke whale (Balaenoptera acutorostrata). Altogether, 502 anomalies were documented in 494 cases of affected cetaceans, including injuries, skin anomalies, emaciation, and neoplasia. Highest prevalence was noted for injuries (245 incidences) of which a minimum of 44 (17%) were consistent with anthropogenic injuries. Our results suggest that human activities in the Strait of Gibraltar, especially fishing activities, pose a threat, particularly to small and medium-sized cetaceans. We, therefore, recommend stricter management enforcement of existing guidelines and laws, as well as the implementation of an area-wide management plan.

Weitere Ausarbeitungen / Publikationen anschauen …

Stiftung firmm

Die Stiftung firmm setzt sich aktiv für die Erforschung und den Schutz von Walen und Delfinen und ihres Lebensraums Meer ein.

Unser Standort Tarifa an der Straße von Gibraltar dient als Forschungs­station und bietet allen Besuchern die Möglich­keit, die faszinierenden Meeressäugetiere in ihrem natürlichen Lebens­raum zu erleben.

firmm Forschungsberichte 2001 bis 2019

firmm Forschungsberichte 2001 bis 2019

firmm Forschungsberichte
2001 bis 2019

Jährlicher Forschungsrückblick der Stiftung, firmm

Jörn Selling, firmm, Tarifa

Stiftung firmm

Die Stiftung firmm setzt sich aktiv für die Erforschung und den Schutz von Walen und Delfinen und ihres Lebensraums Meer ein.

Unser Standort Tarifa an der Straße von Gibraltar dient als Forschungs­station und bietet allen Besuchern die Möglich­keit, die faszinierenden Meeressäugetiere in ihrem natürlichen Lebens­raum zu erleben.

Fin Whales off Gibraltar

Fin Whales off Gibraltar

Fin Whales off Gibraltar

Kongress-Poster von Jörn Selling, firmm

Präsentation zur ECS-Konferenz (ECS = european cetacean society) 2007
(in Englisch)

Die Publikation ist zum Download freigegeben:

Abstract

Most fin whales are believed to stay in the Mediterranean Sea all year round. The population of approximately 3000 individuals is genetically distinct from the North Atlantic population. Some fin whales have also been reported to migrate through the Strait of Gibraltar, possibly connecting both populations. Analysis of iodine content of blubber oil and of carbon isotopes from the baleen plates revealed that some individuals may feed on both Mediterranean and Atlantic krill. Satellite tagging exposed one individual migrating from the Ligurian Basin to northern Portugal. During the summer seasons from 1999 to 2006, an attempt was made to quantify the migration of the whales from the sighting data taken on board of a whale watching vessel from Tarifa. The first step was to estimate the number of migrating fin whales, which was done by extrapolating data from sightings, corrected for effort to 24 hours of whale watching activity. The second step was to calculate an absolute number of whales using the model of ship strikes developed by Dr Tregenza. Considering the resumption of Icelandic commercial whaling and the resulting potential catch of Mediterranean fin whales, it is important for management purposes to know the amount of migrating whales. This is especially true in view of the possibility that those fin whales might be the remaining animals of a former Gibraltar population.

Stiftung firmm

Die Stiftung firmm setzt sich aktiv für die Erforschung und den Schutz von Walen und Delfinen und ihres Lebensraums Meer ein.

Unser Standort Tarifa an der Straße von Gibraltar dient als Forschungs­station und bietet allen Besuchern die Möglich­keit, die faszinierenden Meeressäugetiere in ihrem natürlichen Lebens­raum zu erleben.

Evolution of a unique and ambiguous relationship between Orcas, Pilot Whales and Tuna-fishermen in the Strait of Gibraltar

Evolution of a unique and ambiguous relationship between Orcas, Pilot Whales and Tuna-fishermen in the Strait of Gibraltar

Evolution of a unique and ambiguous relationship between Orcas, Pilot Whales and Tuna-fishermen in the Strait of Gibraltar

Kongress-Poster von Jörn Selling, firmm

Präsentation zur ECS-Konferenz (ECS = european cetacean society) 2011
(in Englisch)

Die Publikation ist zum Download freigegeben:

Abstract

Every summer season killer whales come into the Strait of Gibraltar to interact with fishermen in order to get tuna fishes from the hooks. This interaction evolved two decades ago, when fishermen started to use drop-lines. Sighting-data taken from whale-watch boats from 1999 – 2010, show that the arrival of the orcas correlates with a reduction in sightings of pilot whales, as if they panic. The pilot whales return, but their group-size increases simultaneously when orcas are sighted more regularly between the fishermen in the Strait. There are two spots where fishermen use to gather for tuna fishing. The southernmost is only used by Moroccan boats. At the end of the summer the pilot whales can be observed there starting to chase the orcas out of what they consider their territory. This unique behaviour has been documented in the movie “The Last Giants”. Due to reduced quota given to the drop-line fishermen, that take tuna when it comes back from the Mediterranean after spawning, the season for the orcas is getting shorter. In order to conserve this unique interaction between killer whales, pilot whales and fishermen, it is suggested to increase the quota for drop-line fishermen and instead reduce it for other more harming techniques like purse seines or Almadrabas (pound nets), the latter taking tuna on their way to their spawning grounds in the Mediterranean. This will improve the situation of killer whales, local fishermen and whale watching operators and at the same time reduce the pressure on the spawning stock of Mediterranean bluefin tuna.

Stiftung firmm

Die Stiftung firmm setzt sich aktiv für die Erforschung und den Schutz von Walen und Delfinen und ihres Lebensraums Meer ein.

Unser Standort Tarifa an der Straße von Gibraltar dient als Forschungs­station und bietet allen Besuchern die Möglich­keit, die faszinierenden Meeressäugetiere in ihrem natürlichen Lebens­raum zu erleben.