Fish species abundance and distribution in The Gambia estuary

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Temperature °C32313029282726252423223226 Nov-01 Dec. 20002-12/6/2001Darboe30Temperature282624223216-25/9/2001Temperature °C3028262422Temperature °C323028263-12/12/200124223215-24/4/2002Temperature °C30282624221 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43StationFigure 3: Surface and bottom water temperatures from the five surveys of the Gambiaestuary.During survey 4 (3 – 12 December 2001), recorded temperatures ranged between27.2 o C (station 40, Bantanto Creek) in the upper estuary and 24.0 o C (station 6, Laminpoint in the upper estuary with a mean temperature of 25.48 o C ± 0.7285 o C. Thebottom readings followed a similar pattern with slightly lower values. The meanrecorded was 25.24 o C ± 0.63 o C.The mean surface temperature readings in survey 5,15-24 April 2002, was 26.71 o C ±0.87 o C with the highest temperature of 30.0 o C being recorded at station 15(Tankular)UNU – Fisheries Training Programme 12
Darboeand the lowest, 23.8 o C, at station 2(Banjul). Only slight oscillations were observed atthe rest of the stations with a bottom mean temperature of 26.07 o C ± 0.66 o C.4.1.2 SalinityBoth surface and bottom salinity readings were taken. Records of this parameterduring all the surveys indicate low upstream values (Figure 3). The slope howeverdiffered from survey to survey. During the survey in June (survey 2) the surfacevalues recorded ranged from between 38.5 and 2.5 ppt, between Sika point (station 7)and Deer Island (station 43). In June (at the end of the dry season and beginning of therainy season), the influence of Oceanic tide extended the estuarine condition furthestinland. A scenario of contracting estuary was observed during the following survey inthe third month of the rainy season 16-25 September 2001 (survey 3), when bothbottom and surface salinity read zero at the mouth of Katchang creek (station 20).In December 2000 (survey 4) an upstream movement of the saline front was observedreaching station 23. The highest value recorded, 32 ppt, was at station 2 (Banjul). Itappeared that December-January marked the beginning of reducing fresh waterdischarge into the estuary. Salinity recorded in April, four months later did not onlyindicate an increase in value and elaboration of estuary conditions further inland, butan extreme value of 40 ppt (which is higher than the mean ocean salinity) aroundstations 1 – 3 at the mouth of the estuary. The economic importance of this highsalinity at the lower estuary will be further discussed in later sections.UNU – Fisheries Training Programme 13
Page 3 and 4: DarboeLIST OF FIGURESFigure 1: Map
Page 5 and 6: DarboeShrimp harvests are purchased
Page 7 and 8: Darboe2 LITERATURE REVIEW2.1 Genera
Page 9 and 10: Darboe3 MATERIALS AND METHODS3.1 Or
Page 11: Darboe4 RESULTSThe area covered by
Page 15 and 16: DarboeFigure 6: Distribution of Syn
Page 17 and 18: Dissoled oxygen (mgl-1)7,56,55,54,5
Page 19 and 20: DarboeStation0135791113151719212325
Page 21 and 22: Darboeother surveys), the zone of t
Page 23 and 24: Darboe25201510501/12/200025202-12/6
Page 25 and 26: DarboeFigure 14: Aggregated number
Page 27 and 28: Darboeexplanation for low oxygen co
Page 29 and 30: DarboeACKNOWLEDGEMENTSI express gra
Page 31 and 32: DarboeAPPENDIX : TABLES OF DATA REC
Page 33 and 34: DarboeTable 3: Records of environme
Page 35 and 36: DarboeTable 5: Species occurrence a
Page 37 and 38: DarboeTable 7: Species occurrence a
Page 39 and 40: DarboeTable 9: List of fish epecies

Fish species abundance and distribution in The Gambia estuary

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