Weight-length relationships (WLRs) and relative condition factors were estimated for 9 freshwater fish species from the White Volta, Ghana. Using W=aTLb, the weight-length relationships of the ...species were calculated. Relative condition factors of the species were obtained using the formula: observed weight (Wo)/calculated weight (Wc).The W/L of all the 9 fish species were highly significant (P<0.001). Coefficient of determination (r2) ranged between 0.5764 for Parailia pellucida and 0.9784 for Hydrocynus forskali. The b values of the WLRs of the 9 species ranged from 2.0045 to 3.1614 with 95% confidence interval of b for all the nine fish species within 1.386–3.352. Four out of the 9 species exhibited isometric growth (b=3).Three were observed to have negative allometric growth (b<3) and 2 fish species had positive allometric growth (b>3) patterns. Mean relative condition factors of the species ranged from 1.00 to 1.09. T-test of the observed weight (Wo) versus calculated (Wc) on all the 9 species produced no significant difference (P>0.05) between observed weight and calculated weight. The models are thus good proxies for approximating the weights of the species. Even though, not all species exhibited isometric growth, the general wellbeing of the species was suitable during the study period.
This study investigates the ecology of monogenean gill parasites of Astyanax altiparanae Garutti & Britski, 2000 and Rhamdia quelen (Quoy & Gaimard, 1824) in a stretch of the São Francisco Verdadeiro ...River, Paraná, Brazil. Statistical and ecological indices were used to examine observed levels of parasitism in relation to host and environmental characteristics. A. altiparanae and R. quelen had infestation intensities of 2.8 and 23.1 parasites per fish, respectively. The only significant environmental influence was observed at the upstream station for R. quelen. For both host species, parasitized and non-parasitized individuals presented similar weight-length relationships. Parasitized individuals had dispersed Kn values indicating abnormal conditions. The low levels of parasitism observed in this study suggest that the environment is relatively undisturbed. Additional studies should compare these two species and their respective parasites following completion of the hydroelectric headquarters planned for construction in this stretch of the São Francisco Verdadeiro River.
Cette étude s’intéresse à l’écologie des monogènes parasites des branchies d’Astyanax altiparanae Garutti & Britski, 2000 et de Rhamdia quelen (Quoy & Gaimard, 1824) dans une partie du fleuve São Francisco Verdadeiro, Paraná, au Brésil. Des indices statistiques et écologiques ont été utilisés pour mesurer les taux de parasitisme observés chez l’hôte en fonction de son environnement. A. altiparanae et R. quelen avaient des taux d’infestation de 2.8 et 23.1 parasites par poisson, respectivement. La seule influence environnementale notable sur ce taux a été observée pour R. quelen dans la partie haute du cours d’eau. Pour les deux espèces hôte, les individus parasités et nonparasités présentaient des rapports poids/longueur semblables. Les faibles taux de parasitisme observés dans cette étude suggèrent que l’environnement est relativement peu perturbé. Des études supplémentaires devront comparer ces deux espèces et leurs parasitismes respectifs après l’achèvement des travaux de contruction de barrages hydroélectriques prévus sur ce fleuve.
Bu araşt ı rmada, Ankara-Dikilitaş Göleti'ndeki tatl ı su istakozları n ı n populasyon büyüklü ğü, yoğunluğ u ve biyomas ı , eşey grupları na göre boy ve ağı rl ı k kompozisyonları , boy-a ğı rl ı k ...ilişkileri, sağ l ı k durumu ve tuzak ba şı na av verimi incelenmiştir. Populasyon büyüklü ğ ünün tahmininde, markalama-tekrar yakalama yöntemi Petersen Yöntemi kullan ı lm ışt ı r. Populasyon büyüklü ğünün tahmini için 08.10.1999 ve 12.10.1999 tarihlerinde s ı ras ı yla 1500 ve 1639 tatl ı su istakozu suda ç ı kmayan boya ile markalanm ıştı r. 12.10.1999 ve 15.10.1999 tarihlerinde, markal ı bireylerin %6,87 ve %6,77'si tekrar yakalanm ış ve populasyon büyüklü ğü markalama tarihlerine göre s ı ras ı yla 23843±2185 21658-26028 ve 18011±1567 16444-19578 istakoz olarak tahmin edilmi ştir. Dikilitaş Göleti'ndeki istakozlar ı n yoğ unluğ u ve biyomas ı , I. deneme için 199 180-217 birey/ha ve 6,47 5,88-7,06 kg/ha, Il. deneme için ise 150 137-163 birey/ha, 4,91 4,49-5,34 kg/ha olarak hesaplanm ışt ı r. Populasyonda 75-145 mm aras ı nda dağı l ı m gösteren ortalama 102,26±0,24 mm boy de ğerinin eşey gruplar ı na göre erkeklerde 102,50±0,35 mm ve di şilerde ise 102,04±0,34 mm olduğu ve 90 mm'den küçük bireylerin populasyonun %22,62'sini olu şturduğu belirlenmiştir. Populasyonda 10,00-92,50 g aras ı nda dağı l ı m gösteren ortalama 32,66±0,24 g a ğı rl ı k değerinin eşey gruplar ı na göre erkeklerde 33,11±0,35 g ve dişilerde 32,24±0,33 g oldu ğ u saptanm ışt ı r. Toplam boy-vücut ağı rl ığı ilişkisi erkeklerde W=3*10-5*L3,0092 r=0,9944, n=2122 ve dişilerde W=2"10-5*L3 ' 0 ' 97 r=0,9950, n=2298 olarak belirlenmiştir. Araşt ı rma süresince Dikilita ş Göleti'nden elde edilen birim istakoz av ı , 2,23±0,08 istakoz/tuzak/gün olarak hesaplanm ıştı r. Istakozlar ı n makroskobik incelenmesi sonucunda hastal ı k semptomu ta şı d ı kları kan ı s ı na var ı lm ış ve hastal ı k!' bireylerin oran ı %3,01 olarak belirlenmiştir
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