The trophic ecology of parrotfish of Zanzibar application of stable isotope analysis
- Authors: Plass-Johnson, Jeremiah Grahm
- Date: 2012
- Subjects: Parrotfishes -- Tanzania -- Zanzibar , Parrotfishes , Parrotfishes -- Ecology -- Tanzania -- Zanzibar , Parrotfishes -- Behavior -- Tanzania -- Zanzibar , Parrotfishes -- Food -- Tanzania -- Zanzibar , Scleractinia -- Tanzania -- Zanzibar , Algae -- Tanzania -- Zanzibar , Coral reefs and islands -- Tanzania -- Zanzibar , Coral reef fishes -- Tanzania -- Zanzibar , Stable isotopes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5789 , http://hdl.handle.net/10962/d1005477 , Parrotfishes -- Tanzania -- Zanzibar , Parrotfishes , Parrotfishes -- Ecology -- Tanzania -- Zanzibar , Parrotfishes -- Behavior -- Tanzania -- Zanzibar , Parrotfishes -- Food -- Tanzania -- Zanzibar , Scleractinia -- Tanzania -- Zanzibar , Algae -- Tanzania -- Zanzibar , Coral reefs and islands -- Tanzania -- Zanzibar , Coral reef fishes -- Tanzania -- Zanzibar , Stable isotopes
- Description: Parrotfish are a critical component of the herbivore functional group on tropical coral reefs around the world because they mediate competition that occurs between algae and scleractinian corals. Also, because of their feeding technique, which consists of rasping at the substratum with their beak-like teeth, they play an important role in carbonate turnover and the clearing of reef surface area for the settlement of new sessile organisms. Because of these roles, parrotfishes are an important structuring component of coral reef communities. However, individual species can play different roles depending on their physiology, behaviour and ecology. Despite the possible ecological differences that may exist amongst species, specific roles of the fishes remain unclear as the group is most often studied at higher community levels. This thesis applied stable isotope analysis to differing levels of organisation within a parrotfish community to help elucidate their trophic ecology on coral reefs in Zanzibar. Firstly, blood and muscle tissues were compared to identify differences in their isotope signatures. In other organisms, blood turns over faster than muscle tissue so that muscle tissue represents the diet as integrated over a longer period of time. In most species of parrotfish the blood and muscle δ¹³C signatures were not found to be significantly different, but the δ¹⁵N signatures were significantly different between tissues. This indicated that the δ¹³C signature of both tissues would reveal similar dietary information. Conversely, differences in the δ¹⁵N signature indicated that the nitrogen relationship between tissues was more complicated. Secondly, spatial variability in parrotfish, coral, detritus and macroalgae isotope signatures was assessed at different scales. In macroalgae and coral tissues (zooxanthellae and polyp treated separately), the δ¹³C signatures were shown to differ with depth, presumably because of changes in photosynthetic processes related to depth-associated changes in light. While δ¹⁵N signatures were not affected by depth, all organisms showed enrichment at the Nyange reef, the closest reef to the capital of Zanzibar, Stone Town, presumably reflecting the effects of sewage outfall. These results show that processes that impact the δ¹⁵N signatures of primary producers (macroalgae and zooxanthellae) can be traced to higher trophic levels (coral polyps and fish). Lastly, δ¹³C and δ¹⁵N signatures were used to identify ontogenetic dietary changes in multiple species of parrotfish. Four of the species showed stages that varied from the diets that are normally assumed on the basis of their dentition and feeding technique. This indicates that functional roles based on taxonomy or morphology may fail to include possible ontogenetic dietary changes, and may also fail to elucidate the full impact a species could have on coral reef communities. The conclusions from these studies indicate that the species-specific ecological role of parrotfish in coral reef communities can be complex within and between species, and may differ amongst reefs. In light of the natural and anthropogenic pressures that affect coral reef systems, management decisions based on a more complete understanding of the role of these fish in coral reef communities will help decisions that maintain resilience in these fragile systems.
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- Date Issued: 2012
The Parrot fishes of the Family Callyodontidae of the Western Indian Ocean
- Authors: Smith, J.L.B. (James Leonard Brierley), 1897-1968
- Date: 1956
- Subjects: Western Indian Ocean , Parrotfishes , Callyodontidae , Parrot fishes , Scaridae
- Language: English
- Type: Text
- Identifier: vital:14964 , http://hdl.handle.net/10962/d1018535 , Ichthyological Bulletin; No. 1
- Description: Parrot fishes are so abundant in the tropical parts of the Western Indian Ocean as to be of considerable economic significance. The majority are taken in traps and nets, some by spearing, fewer on lines. The flesh of even the largest is delicate and tasty, mostly eaten fresh as it is not easily preserved. It is esteemed by almost all races and classes, excepting only the Portuguese of Mozambique who do not regard these gaudy fishes with favour. In British territories, however, they are eagerly sought by the Whites. It has been stated that in some parts Parrot fishes are toxic, but as far as could be ascertained no species are ever unwholesome in East Africa or north of Madagascar to Seychelles. It is only in certain specific cases that laymen and even the native fishermen are able to distinguish individual species of Parrot fishes. Most species are more or less lumped together as “Parrots” with prefixes such as “Green” or “Red.” To the native fishermen they are known as follows: Red Sea to Suez, “Harid”; Somaliland, “Jello” or “Ponno”; Kenya to North Mozambique, “Pono”; Seychelles and vicinity, “KAKATOI”; Mauritius, “KAKATOI” or “GATEAU,” some species characterised more closely by descriptive adjectives. These fishes are commonly subject to what appears to be a parasitic infection of the nostrils, resulting in considerable swelling of the snout. , Rhodes University Libraries (Digitisation) , The main funds were provided by the South African Council for Scientific and Industrial Research, enabling expeditions to be made to Mozambique, Tanganyika, Zanzibar, Pemba, Kenya, Seychelles and the other islands north of Madagascar, whose authorities provided valuable aid and facilities in support. It had been intended to include French territories but this was unfortunately not possible. This publication and its ample colour illustration have been made possible by a generous special grant from the South African Council for Scientific and Industrial Research.
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- Date Issued: 1956