Browsing by Author "Kamukuru, Albogast T."

Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    The Distribution, Biological Characteristics and Vulnerability of the Giant Sea Catfish, Arius thalassinus (Rüppell, 1837), to Fishing at Mafia Island, Tanzania
    (2015) Kamukuru, Albogast T.; Tamatamah, Rashid A.
    The distribution and some biological characteristics of commercially important giant sea catfish, Arius thalassinus (Rüppell, 1837) were studied at Mafia Island. Artisanal fishing catches were sampled, caught mainly with longlines, shark nets and ring nets. These yielded a total of 2 723 kg of A. thalassinus, comprising 756 individuals, the largest measuring 1 000 mm TL. Arius thalassinus occurred only on the western coast of Mafia Island and the highest catch rate was 19.3 kg.fisher-1.day-1 in March when murky water was predominant. The reproductive biology of A. thalassinus was investigated to assess its vulnerability to fishing. Arius thalassinus reached a size at first maturity (LM50) of 520 mm TL and exhibited a low mean (±SE) fecundity of 65.6 ± 3.37 eggs per female within the size range of 605-970 mm TL. The hydrated oocytes were large (mean diameter ±SE = 15.2±0.12 mm). Arius thalassinus spawned once in the study year during February and April, during heavy precipitation (124-499 mm). We therefore conclude that its restricted distribution, large size, low fecundity, late maturation and its reported high trophic level indicate that it would be vulnerable to fishing pressure. It is therefore recommended that fishing for A. thalassinus be restricted during its spawning season to ensure its sustainability
  • Thumbnail Image
    Item
    Seagrass - Sea urchin interaction in shallow littoral zones of Dar es Salaam, Tanzania
    (Wiley Online Library, 2008-07) Mamboya, Florence; Lugomela, Charles; Mvungi, Esther F.; Hamisi, Mariam; Kamukuru, Albogast T.; Lyimo, Thomas J.
    Seagrasses biomass, canopy height, shoot density, percentage cover, and sea urchin abundance wereintermittently (between July and November 2007) studied at four littoral sites in the Dar es Salaam area(Mjimwema, Mbweni, Bongoyo Island and Mbudya Island) in order to investigate the seagrass–sea urchinassociation.2. Seagrass biomass ranged from 126.7765.62 g dwt m2in the upper sub-tidal area at Bongoyo Island to508.17133.4 g dwt m2in the upper sub-littoral area at Mbudya Island. Canopy height ranged from6.5172.76 cm in the mid-littoral zone at Mjimwema to 23.878.93 cm in the upper sub-littoral zone atMbudya Island. Shoot densities ranged from 363.67268.9 shoots m2in the mid-littoral zone at Mjimwema to744.07466.9 shoots m2in the lower littoral zone at Mbudya Island.3. Seagrass biomass, canopy height and percentage cover differed significantly among study sites (P 5 0.001,0.0001, 0.008 respectively). However, there was no significant difference in shoot density among the sites(P 5 0.376).4. Ten species of sea urchins were recorded, Echinometra mathaei being the most abundant followed byTripneustes gratilla. Total sea urchin abundance was significantly different among the study sites (P 5 0.001).Seagrass–sea urchin interaction was depicted by significant negative correlations between sea urchin densitieswith seagrass biomass, canopy height, shoot density and percentage cover. This suggests that grazing by seaurchins might have contributed to the reduction of above ground seagrass biomass in locations with higher seaurchin densities. However, further studies are required to corroborate the present results and assess effects ofother factors (e.g. light, nutrients and currents), which also influence seagrass growth.
  • Thumbnail Image
    Item
    Seagrass - Sea urchin interaction in shallow littoral zones of Dar es Salaam, Tanzania
    (Wiley, 2009) Mamboya, Florence; Lugomela, Charles; Mvungi, Esther; Hamisi, Mariam; Kamukuru, Albogast T.; Lyimo, Thomas J.
    Seagrasses biomass, canopy height, shoot density, percentage cover, and sea urchin abundance wereintermittently (between July and November 2007) studied at four littoral sites in the Dar es Salaam area(Mjimwema, Mbweni, Bongoyo Island and Mbudya Island) in order to investigate the seagrass–sea urchinassociation.2. Seagrass biomass ranged from 126.7765.62 g dwt m2in the upper sub-tidal area at Bongoyo Island to508.17133.4 g dwt m2in the upper sub-littoral area at Mbudya Island. Canopy height ranged from6.5172.76 cm in the mid-littoral zone at Mjimwema to 23.878.93 cm in the upper sub-littoral zone atMbudya Island. Shoot densities ranged from 363.67268.9 shoots m2in the mid-littoral zone at Mjimwema to744.07466.9 shoots m2in the lower littoral zone at Mbudya Island.3. Seagrass biomass, canopy height and percentage cover differed significantly among study sites (P 5 0.001,0.0001, 0.008 respectively). However, there was no significant difference in shoot density among the sites(P 5 0.376).4. Ten species of sea urchins were recorded, Echinometra mathaei being the most abundant followed byTripneustes gratilla. Total sea urchin abundance was significantly different among the study sites (P 5 0.001).Seagrass–sea urchin interaction was depicted by significant negative correlations between sea urchin densitieswith seagrass biomass, canopy height, shoot density and percentage cover. This suggests that grazing by seaurchins might have contributed to the reduction of above ground seagrass biomass in locations with higher seaurchin densities. However, further studies are required to corroborate the present results and assess effects ofother factors (e.g. light, nutrients and currents), which also influence seagrass growth.
  • Thumbnail Image
    Item
    Seagrass - Sea Urchin Interaction in Shallow Littoral Zones of Dar es Salaam, Tanzania
    (Wiley, 2009-06) Mamboya, Florence; Lugomela, Charles; Mvungi, Esther; Hamisi, Mariam; Kamukuru, Albogast T.; Lyimo, Thomas J.
    .Seagrasses biomass, canopy height, shoot density, percentage cover, and sea urchin abundance were intermittently (between July and November 2007) studied at four littoral sites in the Dar es Salaam area (Mjimwema, Mbweni, Bongoyo Island and Mbudya Island) in order to investigate the seagrass–sea urchin association.2.Seagrass biomass ranged from 126.7±65.62 g dwt m−2 in the upper sub-tidal area at Bongoyo Island to 508.1±133.4 g dwt m−2 in the upper sub-littoral area at Mbudya Island. Canopy height ranged from 6.51±2.76 cm in the mid-littoral zone at Mjimwema to 23.8±8.93 cm in the upper sub-littoral zone at Mbudya Island. Shoot densities ranged from 363.6±268.9 shoots m−2 in the mid-littoral zone at Mjimwema to 744.0±466.9 shoots m−2 in the lower littoral zone at Mbudya Island.3.Seagrass biomass, canopy height and percentage cover differed significantly among study sites (P=0.001, 0.0001, 0.008 respectively). However, there was no significant difference in shoot density among the sites (P=0.376).4.Ten species of sea urchins were recorded, Echinometra mathaei being the most abundant followed by Tripneustes gratilla. Total sea urchin abundance was significantly different among the study sites (P=0.001). Seagrass–sea urchin interaction was depicted by significant negative correlations between sea urchin densities with seagrass biomass, canopy height, shoot density and percentage cover. This suggests that grazing by sea urchins might have contributed to the reduction of above ground seagrass biomass in locations with higher sea urchin densities. However, further studies are required to corroborate the present results and assess effects of other factors (e.g. light, nutrients and currents), which also influence seagrass growth. Copyright © 2009 John Wiley & Sons, Ltd.