Ecological Aspects of Demersal Tropical Fishes off East Africa

Morgans, J. F. C.

doi:10.1038/193086a0

Cited by 6 publications

(7 citation statements)

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“…However, spawning may occur during the other monsoonal shift occurring SeptemberOctober. There is limited evidence that bimonsoonal spawning occurs for some species and locations in the Western Indian Ocean (Morgans, 1962;Nzioka, 1979;Ntiba and Jaccarini, 1990), but other evidence suggests otherwise (McClanahan, 1988). Courtship behavior of P. areoloatus was similar to that of P. leopardus observed on the Great Barrier Reef, Australia by Samoilys and Squire (1994).…”

Section: Cheilinus Undulatusmentioning

confidence: 73%

Grouper and Napoleon Wrasse ecology in Laamu Atoll, Republic of Maldives: Part 2. Timing, location, and characteristics of spawning aggregations

Sluka¹

2000

Atoll Research Bulletin

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The reproductive ecology of five species of grouper and the Napoleon wrasse was studied March-June, 1998 in Laamu Atoll, Republic of Maldives. Research focused on identifying the timing, location, and characteristics of spawning aggregations in this atoll.Timed surveys were used to assess fish abundance and size distribution in Mundoo Channel, which is one of seven channels connecting Laamu Atoll's inner atoll lagoon to the open ocean. Through a pilot study, and later confirmed in the main study, it was concluded that observations could be conducted and compared over different times of the day, tidal cycles, current speeds, and among observers.A spawning aggregation of Plectropomus areolatus, defined as a three-fold abundance increase over ambient levels, was recorded in Mundoo Channel during the new moon in April, 1998. Data collected during the pilot study suggested that an aggregation occurred in this channel during March, 1998. Courtship behavior for this species was recorded during these two months. Data suggested that P. laevis spawned during this time period as well. Spawning was never observed, but abundance increases and courtship behavior indicate that spawning occurred during this time.

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Section: Cheilinus Undulatusmentioning

confidence: 73%

Grouper and Napoleon Wrasse ecology in Laamu Atoll, Republic of Maldives: Part 2. Timing, location, and characteristics of spawning aggregations

Sluka¹

2000

Atoll Research Bulletin

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“…Possibly water conditions at the turn of the monsoon, when the rains occur, are optimal for this activity. Work on other demersal fish in this area has indicated an increased amount of breeding activity during or just after the rainy seasons and in some cases also in the north-east monsoon (Morgans, 1962(Morgans, , 1964Talbot, 1960;Wheeler & Ommanney, 1953). Pelagic fish of this region show this pattern more clearly (Merrett & Thorpe, 1965;Williams, 1953Williams, , 1956Williams, , 1959Williams, , 1962aWilliams, , 1962bWilliams, , 1965Williams & Newell, 1957).…”

Section: Discussionmentioning

confidence: 99%

“…This was primarily due to the fishing methods used and their location. Morgans (1962) employed bottom lines in 20-30 fathoms (40-60 m) on the North Kenya Banks and caught mainly representatives of the families Lutianidae, Serranidae and Lethrinidae. Talbot (1960) working in and around coral reefs used a wide variety of gear (including gill nets of an unspecified mesh size) and caught mostly lutianids.…”

Section: Introductionmentioning

confidence: 99%

“…Talbot (1960) working in and around coral reefs used a wide variety of gear (including gill nets of an unspecified mesh size) and caught mostly lutianids. In this survey large gill nets (6 and 8 inch stretched mesh and some 4 inch nets) were used in shallower water compared with Morgans' (1962Morgans' ( , 1964 survey. Some lutianids, serranids and lethrinids were caught in the present survey but did not constitute a major element of the catch.…”

Section: Introductionmentioning

confidence: 99%

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Availability, morphometrics, feeding and breeding activity in a multi‐species, demersal fish stock of the Western Indian Ocean

Darracott

1977

Journal of Fish Biology

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A multi‐species demersal fish stock was studied from April 1969 to July 1970. The common species are described in this paper and consist of Carcharhinus sealei, Rhynchobatus djeddensis, Dasyatis kuhlii, Rachycentron canadum, Psettodes erumei and Arius sp. With the exception of Rachycentron canadum, these fish were available throughout the year and some coincidence of increased availability was noted in August/September. Psettodes erumei, the commonest fish caught, was most available in August/September, February/ March and June. The size and weight distribution of each of these fish is described. Morphometric results indicate that two fish, Dasyatis kuhlii and Psettodes erumei, exhibit sexual dimorphism, the females being larger and heavier than the males. Carcharhinus sealei, Rhynchobatus djeddensis and Rachycentron canadum have a nearly isometric growth exponent whereas Dasyatis kuhlii, Psettodes erumei and Arius sp. have an allometric growth exponent. All fish were carnivores, Rhynchobatus djeddensis, Rachycentron canadum and Arius sp. being primarily crustacean feeders, Dasyatis kuhlii feeding on polychaetes and crustaceans and Carcharhinus sealei and Psettodes erumei feeding mainly on fish. The increased number of all three bony fish noted in August/September (immediately prior to the short rains in October/November) is discussed in relation to feeding activity and the initiation of spawning activity. It is suggested that spawning in Psettodes erumei and Arius sp. is initiated in September, continuing possibly to February and then during the long rains (March/May) and the South East Monsoon the fish recover. It is also suggested that pregnant elasmobranchs may come inshore in greater numbers during the rains to give birth.

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“…Studies on seasonal catches of finfish in Tanzania have shown that the catch is low during the Southeast monsoon and high during the Northeast monsoon with a peak in March at the end of the NE monsoon (Newell, 1957;1959;Morgans, 1962;McClanahan, 1988). The seasonality was attributed to fish migrations and decreased density and activity due to a deeper thermocline and cooler waters in the Southeast monsoon (Newell, 1957;McClanahan, 1988).…”

Section: Catch Ratesmentioning

confidence: 99%

The Fishery of <i>Portunus pelagicus</i> and Species Diversity of Portunid Crabs along the Coast of Dar es Salaam, Tanzania

Chande

Mgaya

2004

West Ind. Oc. J Mar. Sci.

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Abstract-Production, habitat preference and distribution of the blue swimming crab, Portunus pelagicus and the diversity of portunid crabs were studied along the Dar es Salaam coastline, Tanzania. Samples were obtained from beach seine nettings and basket traps. The samples from basket traps were used in habitat preference studies only. The production of Portunus pelagicus was assessed in terms of catch rate and biomass, and the biomass and contribution of recruits to the stock estimated using the Leslie method. Seasonal variations in catch rate were found, with peaks between December and May. The highest catch rate was recorded at Msasani Bay (2.24 kg/haul/100-m net), and the lowest at Mzinga Creek (1.08 kg/haul/100-m net). The harvestable biomass for Dar es Salaam coast on average was 34.5 tonnes/year, while the contribution of recruitment to the biomass was about 20.2 tonnes/year. Portunus pelagicus was the most abundant portunid in all the sites, comprising between 39.1 and 81.5% of the catches at Mzinga Creek and Kunduchi respectively. Charybdis anisodon, Scylla serrata and Portunus sanguinolentus were also found in various proportions at the sites. Generally there was a significant difference in species diversity between sites, with P. pelagicus showing a high preference for the sub-littoral shallow waters. For rational exploitation of this crab, management measures based on the estimated harvestable biomass and the size at first maturity are recommended.

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Ecological Aspects of Demersal Tropical Fishes off East Africa

Cited by 6 publications

References 1 publication

Grouper and Napoleon Wrasse ecology in Laamu Atoll, Republic of Maldives: Part 2. Timing, location, and characteristics of spawning aggregations

Grouper and Napoleon Wrasse ecology in Laamu Atoll, Republic of Maldives: Part 2. Timing, location, and characteristics of spawning aggregations

Availability, morphometrics, feeding and breeding activity in a multi‐species, demersal fish stock of the Western Indian Ocean

The Fishery of <i>Portunus pelagicus</i> and Species Diversity of Portunid Crabs along the Coast of Dar es Salaam, Tanzania

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