Freshwater fish fauna of Saudi Arabia: causes of population decline and their protection, a case history
Saudi Arabia supports endemic as well as epidemic species of freshwater fish distributed in various parts of the country. The population of some native fish species, like the other fish species in various regions of the world, is declining rapidly. Among the endemic species Aphanius dispar is supposed to be more endangered species because its population is declining in various environment of Saudi Arabia (P. obs.). Conservation studies revealed that individual species in not threatened by a single isolated factor, instead it faces numerous stressors that threatened multiple stages of their life cycle. Protecting fishes will thus help to protect aquatic biodiversity and in conservation of biological heritage of the country.
Studies on reproductive biology of sailfin molly,
Poecilia latipinna (Lesueur, 1821) in Wadi Haneefah stream, Riyadh, Saudi Arabia
The current study addressed the reproductive activity of P. latipinna. Some parameters studied to evaluate this activity included the gonadosomatic index, developmental stages of gonads and observed, calculated and relative fecundity. Relationship between sexual maturity and body length as well as body weight for the both males and females was determined. The sex ratio was also estimated.
The results showed that the mature eggs in ovaries of P. latipinna were found in the month of March to late May and then from month of August to November. This is indicated by the gonadosomatic index recorded high in these months.
The recorded values of gonadosomatic index in the current study show that the first phase of egg-laying for P. latipinna may starts in June and extend till July and the phase begins in December which ends in January as indicated by sharp decline in the values of gonadosomatic index in these periods.
The maturation of gonads in P. latipinna begins at relatively lesser lengths of the male than the females. The males show differences between the various stages of sexual development while females do not show differences between any of these stages in any case.
In general, P. latipinna produces larvae relatively larger in size this is inferred from the large size of eggs laid by females. These larvae are characterized by rapid growth and better resistance to unfavorable environmental conditions which gives them a better chance of survival.
The value of relative fecundity (number of eggs per unit weight or length of the fish) ranges from 12.11 to 19.65 and does not show any regular pattern of variation. The observed and calculated fecundity (number of eggs / female in one season) for P. latipinna ranges from 32.81 – 199.97. It was found that observed fecundity in P. latipinna increase with the increase in weight and the length of the body where smaller fish produces fewer numbers of eggs compared to the large fish. The relationship between observed fecundity of P. latipinna and its weight and length is statistical significance.
The sex ratios of P. latipinna in the current study was estimated as 3:1 in favor of females where the numbers of female registered in the study over numbers the males throughout the year .
Changes in Population density of planktons and Physical-chemical
conditions of Wadi Haneefah Stream, Riyadh, Saudi Arabia
Studies on the qualitative and quantitative variations of phytoplankton and zooplankton populations as well as physical-chemical condition of water at three different locations in Wadi Haneefah Stream was carried out. Water temperature fluctuated between 18.0 °C - 32.0°C where as pH values from 7.1 to 8.5. High concentrations (10.2, 10.8 and 11.2 mgl-1) of dissolved oxygen at the sites I, II and III, respectively, were recorded in May. The contents of chloride, Alkalinity and sulphate were maximum in July-August. It is found that most of the parameters studied such as turbidity, conductivity, hardness, total nitrogen, total dissolved solids, phosphorus, BOD and COD have high values in summer months (June –September).
Different phytoplanktonic genera present at three sites belong to the families, chlorophyceae, cyanophyceae, desmidiaceae and bacillariophyceae. Among all these, bacillariophyceae was the dominating group throughout the study period. The population density of the plankton was more prominent in summer and less during winter season. Protozoans, rotifers and crustaceans were the main groups consisting the zooplankton. These zooplanktons were prominent forming a peak in July and trough in January. Correlation between the population of phytoplankton and zooplankton with the physical and chemical conditions of the environment were deduced.
Studies on Feeding Ecology of Sailfin Molly (Poecilia latipinna) Dwelling in Wadi Haneefah Stream, Riyadh
Feeding ecology of sailfin molly (Poecilia latipinna), an introduced fish species, was studied. Food items recovered from the stomach of fishes exclusively indicated that it is a herbivorous fish. And according to data obtained there is not much difference in the type of food consumed by the fishes of different size groups. Frequency of occurrence of different food items in the diet of fishes of various sizes was high. The value of vacuity index also showed variation throughout the study period. The diet overlap index was high which shows the sharing of food items among the fishes of different size groups. The diet breadth index also showed variations among the fishes of various sizes and in different seasons.
Length – weight relationship and monthly changes in different indices of Oreochromis niloticus
The value of regression co-efficient (3.092) registered in the present study for the combined sexes showed that the cube law is applicable in Oreochromis niloticus species of fish. The value of correlation coefficient (r = 0.987) also showed a strong relation between the total length and gutted weight of the fish. The condition coefficient showed variation in deferent months being high from November to May and low in January, Jun, August and October. Hepatosomatic index and filling index follow the similar pattern of variations. The former ranges from 1.62 (July) to 2.79 (June) whereas latter has a maximum value in October (10.49) and minimum in August (6.27). Gonadosomatic index for male and female showed two troughs, one in the March (male-0.94, female-1.93) and second in September and October (male-0.16, 0.14 and female-1.41, 0.98).
Monthly innovations in haematological
profile and biochemical composition of liver and white muscle of Oreochromis niloticus (Linnaeus, 1758)
The glycogen levels in liver and muscle of O. niloticus were low during spawning period (July and September). The muscle protein was low and that of liver high from June to September, plasma protein being highest in May. Triglyceride was highest in February and falls gradually till September. The plasma glucose was high from July to November, whereas the plasma triglyceride and glycogen were low in these months. Hemoglobin, haematocrit values, erythrocytes and leucocytes counts showed considerable variations throughout.
Toxicity Bioassay, Ethological and Haematological responses and Carbohydrate Metabolism of carp, Cyprinus carpio, Exposed to Trichlorfon.
Al-Ghanim, K. A.; AlKahem-Al-Balawi, H.F.; Al-Akel, A.S.; Al-Mesnad, F.; Ahmad, Z. and Annazri, H.
Specimens of carp, Cyprinus carpio, exposed to different lethal and sublethal concentrations of trichlorfon showed restlessness, excess secretion of mucus, rapid body movements and difficulty in respiration. The Lc50 values along with 95% fiducial lower and upper limit (in parentheses) for 24h, 48h, 72h and 96h, computed from a probit graph, for tested fish were 16.58 mg/l (15.92-17.37), 13.28 mg/l (12.28-14.50), 10.75 mg/l (9.93-11.64) and 8.52 mg/l (7.81-9.26), respectively. Haematological parameters studied showed that the erythrocytes count, haemoglobin concentrations and haematocrit values were increased whereas leukocytes count dropped down after trichlorfon exposure. Values of erythrocytic indices like MCV, MCH, and MCHC were also changed. Differential counts showed that the trichlorfon causes lymphopenia, thrombopenia and Neutrophilia in the toxicant exposed fish. Level of glycogen in muscles and liver of fish were decreased significantly (p<0.05) while glucose level was increased remarkably after pesticide treatment.
Al-Ghanim, K. A. ; Al-Kahem-Al-Balawi, H. F. ; Al-Akel, A. S. ; Al-Mesnad, F. ; Ahmed, Z. and Annazri, H. (2007). Toxicity Bioassay, Ethological and Haematological responses and Carbohydrate Metabolism of carp, Cyprinus carpio, Exposed to Trichlorfon.