Omar A Amir

Marine megafauna interactions with small-scale fisheries in the southwestern Indian Ocean: a review of status and challenges for research and management

Reviews in Fish Biology and Fisheries, 2017

In developing regions, coastal communities are particularly dependent on small-scale fisheries fo... more In developing regions, coastal communities are particularly dependent on small-scale fisheries for food security and income. However, information on the scale and impacts of small-scale fisheries on coastal marine ecosystems are frequently lacking. Large marine vertebrates (marine mammals, sea turtles and chondrichthyans) are often among the first species to experience declines due to fisheries. This paper reviews the interactions between small-scale fisheries and vulnerable marine megafauna in the southwestern Indian Ocean. We highlight an urgent

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Population structure and diversity of Indo-Pacific bottlenose dolphins (Tursiops aduncus) in the western Indian Ocean

Bottlenose dolphin (Tursiops sp.) populations often show small-scale genetic differentiation and ... more

Recent records of marine mammals in Tanzanian waters

J. Cetacean Res. Manage.

Marine mammal species diversity off Zanzibar and Tanzania, East Africa, has been recorded by the ... more Marine mammal species diversity off Zanzibar and Tanzania, East Africa, has been recorded by the Marine Mammal Education and Research Group at the Institute of Marine Sciences, Zanzibar, Tanzania since 1998. The data presented in this report reflect the efforts of 10 years collection of information from marine mammals stranded and incidentally caught in Tanzanian waters. Additional information from dedicated surveys of cetaceans (whales and dolphins) and incidental sightings reported by the general public are also provided. From 1992 through 2008 a total of 235 specimens of 13 cetacean species and the dugong were recorded. 214 (90.7%) records referred to specimens from bycatch in drift and bottom-set gillnets and 22 (9.3%) referred to specimens from strandings. Based on incidental catch and sightings records, Indo-Pacific bottlenose, spinner and Indo-Pacific humpback dolphins, observed year-round, and humpback whales, observed seasonally during July to November, were the most common...

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Vagrant Subantarctic Fur Seal on the Coast of Tanzania

African Zoology, 2010

An immature Subantarctic fur seal was sighted on Unguja Island, Zanzibar, Tanzania, in 2008. This... more An immature Subantarctic fur seal was sighted on Unguja Island, Zanzibar, Tanzania, in 2008. This is the most northerly record of a vagrant of this species. The nearest breeding colony is on the Prince Edward Islands, 4500 km distant. While it is likely that this is the natal site of the vagrant due to its proximity and population size, the actual location of origin is unknown. This is the second fur seal sighted in this area. A fur seal of unknown species was sighted on Pemba Island, 30 km north of the Unguja Island, in 2002. While the species of the latter animal could not be determined, it is likely also a Subantarctic fur seal.

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The incidental catch of dolphins in gillnet fisheries in Zanzibar, Tanzania

Western Indian Ocean journal of marine science, 2002

The level of incidental catches of dolphins in artisanal gillnet fisheries was investigated in a ... more The level of incidental catches of dolphins in artisanal gillnet fisheries was investigated in a questionnaire survey of 101 gillnet vessel operators from 10 villages in Unguja island of Zanzibar, representing half of all the gillnet fishing fleet in 1999. A total of 96 dolphins were reported to have been incidentally caught between 1995 and 1999; 43 Indo-Pacific bottlenose dolphins ( Tursiops aduncus ), 29 spinner dolphins ( Stenella longirostris ), 5 IndoPacific humpback dolphins ( Sousa chinensis ) and 19 unidentified dolphins. Most of these incidental catches (46) were reported in 1999. We extrapolate that 93 animals may have been incidentally caught by the entire fishing fleet (201 vessels) during 1999. This estimate represents a serious cause for concern, suggesting that the incidental capture of dolphins in Zanzibar’s artisanal gillnet fisheries may be high enough as to have a significant negative impact on local populations. Further studies to accurately estimate the total b...

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Marine megafauna interactions with small-scale fisheries in the southwestern Indian Ocean: a review of status and challenges for research and management

In developing regions, coastal communities are particularly dependent on small-scale fisheries fo... more In developing regions, coastal communities are particularly dependent on small-scale fisheries for food security and income. However, information on the scale and impacts of small-scale fisheries on coastal marine ecosystems are frequently lacking. Large marine vertebrates (marine mammals, sea turtles and chondrichthyans) are often among the first species to experience declines due to fisheries. This paper reviews the interactions between small-scale fisheries and vulnerable marine megafauna in the southwestern Indian Ocean. We highlight an urgent need for proper documentation, monitoring and assessment at the regional level of small-scale fisheries and the megafauna affected by them to inform evidence-based fisheries management. Catch and landings data are generally of poor quality and resolution with compositional data, where available, mostly anecdotal or heavily biased towards easily identifiable species. There is also limited understanding of fisheries effort, most of which rel...

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Marine Mammal Bycatch in the Southwest Indian Ocean: Review and Need for a Comprehensive Status Assessment

Incidental catch in fishing gears is a serious, worldwide threat to marine megafauna (particularl... more Incidental catch in fishing gears is a serious, worldwide threat to marine megafauna (particularly sea turtles, sharks and marine mammals). In order to inform the implementationa of effective bycatch management strategies, an important first step is to conduct an assessment of the extent of this threat. In the southwest Indian Ocean (SWIO) (from 0 to 25°S, from eastern Africa to 60°E), there is a paucity of published data describing marine mammal bycatch. This review collates available information from a range of sources relating to marine mammal bycatch for nine SWIO countries: Mozambique, Tanzania (including Zanzibar), Kenya, the Seychelles, the Comoros, Mayotte, Madagascar, Reunion Island and Mauritius. An overview of the bycatch issue within each country is provided by considering the following key points: status of marine mammals, fishing effort, bycatch information and mitigation measures. Quantitative information, especially with respect to number of bycaught animals and impact on local populations, was found to be limited (except for Zanzibar). However, it is clear that several fisheries do incidentally catch marine mammals in the region, those of greatest concern being gillnets catching dugong (Dugong dugon) and coastal dolphins (Tursiops aduncus and Sousa chinensis) in Zanzibar and southwest Madagascar. To date, mitigation measures, particularly efforts to reduce the use of these gears, have not been employed effectively. From the information provided in this review, it is evident that it is critical to initiate the collection of quantitative data for marine mammal bycatch (particularly in gillnets) and its impact on local marine mammal populations and to implement relevant and effective mitigation measures.

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Feeding ecology of the Indo-Pacific bottlenose dolphin (Tursiops aduncus) incidentally caught in the gillnet fisheries off Zanzibar, Tanzania

Estuarine, Coastal and …, 2005

... Omar A. Amir a , b , Corresponding Author Contact Information , E-mail The Corresponding Auth... more

Habitat availability and geographic isolation as potential drivers of population structure in an oceanic dolphin in the Southwest Indian Ocean

by Omar A Amir and Narriman Jiddawi

Marine Biology, 2016

Incidental catch of marine mammals in the southwest Indian Ocean: a preliminary review

1 University of La Rochelle. LIENSS (Littoral, Environnement et Sociétés). UMR 6250 CNRS-Universi... more

The occurrence and distribution of dolphins in Zanzibar, Tanzania, with comments on the differences between two species of Tursiops

by Omar A Amir and Narriman Jiddawi

Western Indian Ocean Journal of Marine Science, 2005

... Ph.D thesis. Department of Zoology, Stockholm University. ISBN 91-7265-837-X Stensland, E., B... more

Sustainable Dolphin Tourism in East Africa

Growth and reproduction of Indo-Pacific bottlenose dolphins (Tursiops aduncus) incidentally caught in gillnets off Zanzibar, Tanzania

by Omar A Amir and Narriman Jiddawi

Life history parameters of Indo-Pacific bottlenose dolphin (Tursiops aduncus) were examined in 69... more

Spatial and Temporal Variations in the Occurrence and Foraging Activity of Coastal Dolphins in Menai Bay, Zanzibar, Tanzania

by Omar A Amir and Narriman Jiddawi

PloS one, 2016

Understanding temporal patterns in distribution, occurrence and behaviour is vital for the effect... more Understanding temporal patterns in distribution, occurrence and behaviour is vital for the effective conservation of cetaceans. This study used cetacean click detectors (C-PODs) to investigate spatial and temporal variation in occurrence and foraging activity of the Indo-Pacific bottlenose (Tursiops aduncus) and Indian Ocean humpback (Sousa plumbea) dolphins resident in the Menai Bay Conservation Area (MBCA), Zanzibar, Tanzania. Occurrence was measured using detection positive minutes. Inter-click intervals were used to identify terminal buzz vocalisations, allowing for analysis of foraging activity. Data were analysed in relation to spatial (location) and temporal (monsoon season, diel phase and tidal phase) variables. Results showed significantly increased occurrence and foraging activity of dolphins in southern areas and during hours of darkness. Higher occurrence at night was not explained by diel variation in echolocation rate and so were considered representative of occurrence...

Estimates of bycatch and field experiment using pingers to reduce bycatch of dolphins in drift- and bottom set gillnets in Menai Bay, Zanzibar, Tanzania

... Create reference ». Author: Amir, Omar A. (Stockholm University, Faculty of Science, Departme... more

Biology, ecology and anthropogenic threats of Indo-Pacific bottlenose dolphins in east Africa

This thesis examines the biology, ecology and anthropogenic threats of Indo-Pacific bottlenose do... more This thesis examines the biology, ecology and anthropogenic threats of Indo-Pacific bottlenose dolphins (Tursiops aduncus) off Zanzibar, Tanzania, based on research conducted and samples collected between 2000 and 2008. Distribution and occurrence are described based on incidental catches (bycatch) in gillnet fisheries. Biology and ecology are examined by ageing and studying the reproductive biology and stomach contents of collected specimens. The composition of organohalogen compounds is determined in blubber samples, and assessment and mitigation of bycatch are conducted using observers onboard fishing vessels. Fisheries bycatch data showed that Indo-Pacific bottlenose dolphins occur year round in all areas around Zanzibar. Sexual maturity was attained between 7 and 8 years and body length 190-200 cm in females and at 16 years and body length 213 cm in males. The gestation period was estimated to be 12.3 months, with calving occurring throughout the year, peaking November-March and with an interval of 2.7 years. The estimated pregnancy rate was between 0.10 and 0.58 depending on methods used. Stomach contents revealed a relatively large number of prey species, but that only a few small-and medium-sized neritic fish and cephalopods contribute substantially to the diet. Estimates of total annual bycatch were >9% which is not considered sustainable. An experiment showed that pingers can be a short term mitigation measure to reduce bycatch of dolphins in both drift-and bottom set gillnets. Methoxylated polybrominated diphenyl ethers (Meo-BDEs) were found at higher concentrations than anthropogenic organic pesticides (OCPs), with only traces of polychlorinated biphenyls (PCBs) detected. This study reveals the magnitude and apparent susceptibility of Indo-Pacific bottlenose dolphins off Zanzibar to anthropogenic threats, especially fisheries bycatch, and it is clear that immediate conservation and management measures are needed to reduce bycatch.

format_quoteHigh levels of harmful substances, like organochlorine pesticides, were detected in dolphin blubber, raising health concerns.format_quote

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The Occurrence and Distribution of Dolphins in Zanzibar, Tanzania, with Comments on the Differences Between Two Species of <i>Tursiops</i>

by Omar A Amir and Narriman Jiddawi

Western Indian Ocean Journal of Marine Science, 2007

... Occurrence and Distribution of Dolphins in Zanzibar, Tanzania, with Comments on the Differenc... more

Integrating multiple lines of evidence to better understand the evolutionary divergence of humpback dolphins along their entire distribution range: a new dolphin species in Australian waters?

Molecular Ecology, 2013

The conservation of humpback dolphins, distributed in coastal waters of the Indo-West Pacific and... more The conservation of humpback dolphins, distributed in coastal waters of the Indo-West Pacific and eastern Atlantic Oceans, has been hindered by a lack of understanding about the number of species in the genus (Sousa) and their population structure. To address this issue, we present a combined analysis of genetic and morphologic data collected from beach-cast, remote-biopsied and museum specimens from throughout the known Sousa range. We extracted genetic sequence data from 235 samples from extant populations and explored the mitochondrial control region and four nuclear introns through phylogenetic, population-level and population aggregation frameworks. In addition, 180 cranial specimens from the same geographical regions allowed comparisons of 24 morphological characters through multivariate analyses. The genetic and morphological data showed significant and concordant patterns of geographical segregation, which are typical for the kind of demographic isolation displayed by species units, across the Sousa genus distribution range. Based on our combined genetic and morphological analyses, there is convincing evidence for at least four species within the genus (S. teuszii in the Atlantic off West Africa, S. plumbea in the central and western Indian Ocean, S. chinensis in the eastern Indian and West Pacific Oceans, and a new as-yet-unnamed species off northern Australia).

Phylogenetic placement and population structure of Indo-Pacific bottlenose dolphins (Tursiops aduncus) off Zanzibar, Tanzania, based on mtDNA sequences

by Omar A Amir and Magnus Danbolt

Marine Mammal Science, 2011

Phylogenetic placement of bottlenose dolphins from Zanzibar, East Africa and putative population ... more Phylogenetic placement of bottlenose dolphins from Zanzibar, East Africa and putative population differentiation between animals found off southern and northern Zanzibar were examined using variation in mtDNA control region sequences. Samples (n = 45) from animals bycaught in fishing gear and skin biopsies collected during boat surveys were compared to published sequences (n = 173) of Indo-Pacific bottlenose dolphin, Tursiops aduncus, from southeast Australian waters, Chinese/Indonesian waters, and South African waters (which recently was proposed as a new species) and to published sequences of common bottlenose dolphin, Tursiops truncatus. Bayesian and maximum parsimony analyses indicated a close relationship between Zanzibar and South African haplotypes, which are differentiated from both Chinese/Indonesian and Australian T. aduncus haplotypes. Our results suggest that the dolphins found off Zanzibar should be classified as T. aduncus alongside the South African animals. Further, analyses of genetic differentiation showed significant separation between the T. aduncus found off northern and southern Zanzibar despite the relatively short distance (approximately 80 km) between these areas. Much less differentiation was found between southern Zanzibar and South Africa, suggesting a more recent common evolutionary history for these populations than for the northern and southern Zanzibar populations.

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Molecular ecology meets remote sensing: environmental drivers to population structure of humpback dolphins in the Western Indian Ocean

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Papers by Omar A Amir