68
Applied studies are related to the experimental studies and these were also very few accounting for 2.7 of all the studies. Mostly they were related to aquaculture experiments such as the cage culture of Siganus spp. Bwathondi,
1981a, the aquaculture of rabbit fish and milkfish in ponds at Makoba Mmochi et al., 1996, 1999 and the experimental culture of oysters, Saccostrea cucccullata, in the habour area of Zanzibar Jiddawi, 1989. Talbot
and Newell 1957 attempted the first study on fish aquaculture in marine ponds in Zanzibar. The fish cultured in the experiment was Tilapia, although Chanos chanos later invaded the ponds and became very successful as well.
These studies have started to have a positive implication among the people in some areas of Tanzania that have shown great interest of establishing mariculture ponds.
3.3.5 Review studies
Most of the fisheries reports that were examined 41 are of review nature. These studies presented the general information on fisheries in different parts of the country and the West Indian ocean region, for example Cushing, 1985, Maembe, 1988;
Jiddawi et al., 1992, 1994, Mhando and Jiddawi, 1998. Several reports discuss fisheries development in the country and priorities for fisheries management Boerema, 1981, FAO, 1982, Ardill, et al., 1991. The reviews also provide information
on the status and trends of exploitation of marine fisheries in Tanzania Bwathondi and Ngoile, 1982; Nhwani, 1983, Bryceson, 1985; Ngoile, 1988,. The reports also review specific fisheries such as the pelagic fisheries Nhwani, 1983,1988
and the demersal fisheries Ngoile, 1982, Pratap, 1982, Bensted-Smith, 1987, Jiddawi, 1997a. Mhitu and Jiddawi, 1999. Environmental conservation in the artisanal fisheries sector has also been reviewed for the Tanzania mainland Mwamsojo,
1999 and in Zanzibar Jabir et al., 1999.
3.3.6 Other type of studies
Fishery resource surveys have been grouped in other type of studies and forms 12 of all the studies. All the fish resource surveys conducted by Research Vessels in Tanzania waters and the region fall under this category. These
surveys include the surveys conducted by Dr Fidjitof Nansen in the 19980s Anon, 1982a; Iversen et al., 1985, the survey by R.V Prof Mestyasev Birkett, 1978, Venema, 1984 and the surveys conducted by Mbegani fisheries
Institute through its research vessel MV Mafunzo Van Nierop, 1987b, Msumi, 1986, 1987, 1988. These surveys provided an insight on the fishery potential and stock abundance in the Tanzanian waters. The Fishery
acts and policies also belong to this category Anon, 1993; Maembe, 1984 as well as sociological and economical studies on fisheries Mapunda1983, Chachage, 1988, Saleh, 1992, Nasser, 1995, Soley, 1997. Studies on shark
trade and fish export Ameir, 1995, Barnett, 1997 and legal aspects of fishing in Tanzania Christy, 1981; Lamwai, 1988, Anon, 1999 have been included in this list.
3.4 Research methodology
This section refers to baseline, observational experimental and applied studies where samples were collected for detailed studies.
3.4.1 Sampling aspects and parameters
Sampling aspects varied according to the studies conducted. In the case of fish resources surveys the parameters measured were temperature, depth, salinity in order to determine the relationship between fish abundance and
availability, size and species distribution with the physical parameters Iversen et al., 1985. For biological studies such as length weight relationship and morphometric studies of fish the parameters measured on the fish
were total length, standard length, fork length, eye diameter, body depth, snout length, and other parts of the body Rubindamayugi, 1983; Mhitu, 1997; Jiddawi, 1999. Other common parameters measured in reproductive studies
include individual weight of fish and visual observation of sex and gonad maturation Mgimwa, 1998, Jiddawi, 1999.
69
Some important parameters collected during the different studies were catch and effort data of the fish during landings in studies related to estimation of fish biomass Jiddawi, 1999. Others were areas fished, weather
conditions, the fishing duration and any other factors that could have an impact on the days fishing such as festival and cultural taboos in fishery descriptive studies Jiddawi and Stanley, 1999.
3.4.2 Instrumentation and techniques of data collection
Sampling techniques varied in the different studies. Whereas in the case of Jiddawi and Stanley 1999, the study involved standing at the landing site and recording details of each, Horst 1999 actually followed the fishermen
as an observer in their fishing boats to assess the performance of the dema trap fishery. In some instances specimen were bought from the fishermen for detailed studies of specific fish. These include the biological and
age and growth studies of the Indian mackerel Rastrelliger kanagurta, Jiddawi, 1999, the biological study of squid Mhitu, 1997 and during the study of the biology of the blue speckled parrotfish Leptoscarus vaigiensis
along the coast of Tanzania, Rubindamayungi, 1983.
Few instruments were employed in fishery studies apart from standard equipment such as the measuring board, the Vernier calipers, weighing scales and portable spring balance. In some several instances the fishing gears
were checked on their efficiency. For example the beach seine net was used as an equipment for catching fish in intertidal areas during the study of the nursery potential of the mangrove ecosystem Muhando and Ngoile, 1995,
Mahika 1992 used grid separators to reduce by catch in the Panaeid fishery. Hydrographical data, such as temperature, salinity and oxygen content were collected using reversible Nankeen water bottles which were
applied in different depths during fish resource surveys. Also, samples from the surface were collected by a buckets Iversen et al., 1985. Fish abundance was investigated acoustically using scientific sounders, integrators
and sonar equipment Iversen et al., 1985. Pelagic trawl hauls were carried out either to identify scattering layers or to investigate the surface layer for fish. Demersal trawl hauls were placed at random in trawlable areas and fish
biomass estimations were made according to the swept area method Anon, 1982, Iversen at al., 1985; 1983; Msumi, 1988.
3.4.3 Sampling frequency and time of collection
