倒刺鲃生活史各阶段的食性分析

Analysis of Food Habits of Spinibarbus denticulatus in Its Life History

2004年3月至2005年2月对分布在西江水系中上游广西柳江段龙江中的一种名贵经济鱼类——倒刺鲃(Spinibarbus denticulatus)生活史各发育阶段的食性进行了分析研究。采用常规生物学方法,测定了倒刺鲃生活史各发育阶段的消化道指数、肠长指数、食物充塞度、肥满度等生物学参数。通过其食物组成、出现率和饵料类群变动或更替的数量特征,细分出倒刺鲃各发育阶段的食性特点:仔鱼和稚鱼阶段为杂食性偏动物食性;早期幼鱼为明显的杂食性;青年鱼则趋向于杂食偏植物食性;成鱼才是真正意义上的草食性鱼类。倒刺鲃幼龄及青年个体在周年中保持2·0～5·0的食物充塞度,而成鱼的摄食强度则存在明显的季节变化,在1月的平均充塞度只有0·3,在10月则为5·0。倒刺鲃幼龄个体周年中肥满度变化不明显,条件系数全年维持在2·201～2·406;青年个体周年中的肥满度5～8月间维持相对稳定,平均条件系数的变幅为2·337～2·365,但从9～12月,条件系数逐渐从2·451逐渐增大到2·852,在1～4月,条件系数逐渐从2·693减小到2·306;成鱼的肥满度呈现明显的季节变化,7月的条件系数为1·775,12月的则高达2·894。在倒刺鲃的整个生活史中,藻类在消化道中的出现率均达100%,平均湿重百分比在25·0%以上,可能是其重要的食物类群。

The present paper deals with the feeding habits of a rare and commercial fish - Down-spine Carp, Spinibarbus denticulatus distributed in the Longjiang River, a section of the Liujiang River, belonging to the mid and upper reaches of the Xijiang River in Guangxi Autonomous Region from Mar. 2004 to Feb. 2005. In its history of life, the larvae fed mainly on algae （i.e. diatoms）, protozoa （i.e. Arcella, Diffugia）, rotifer and copepoda. Algae and rotifer were found to be the most important food item in the gut contents. Besides these, the juvenile fed also on filamentous green algae （ i.e. Cladophora, Spirogyra ）, oligochaetes （ i.e. Tubifex, Limodrilus ）, aquatic insect larva （i. e. Chironomidae ） and detritus. Early young fish was inclined to be omnivorous, as a small amount of larger phytobenthos （ i.e. Chara, Nitella ） and aquatic plants （ i.e. Ceratophyiium de mersum, Hydrilla varticiUata, Potamogeton malainus ） were also added to food components in the gut compared with a diet of the juvenile. The adolescent fish tended to be more herbivorous due to an increase in an amount of aquatic plants. Adult fish was factually herbivorous whose food items in its gut were mostly constituted by such aquatic plants as C. demersum, Myriophyllum spicatum, Najas major, P. malainus, P. crispus and Vallisneria spiralis. Food fullness of grade 2.0 to 5.0 was sustained in the guts of juvenile, early young fish and adolescent fish throughout one year. Seasonal variation of average food fullness in adult fish was distinctively observed with a minimum of grade O. 3 in Jan. and a maximum of grade 5.0 in Oct. Variation in annual fullness with season did not markedly present itself in juvenile and early young fish, which average condition factor （ACF） ranged from 2.201 to 2.406 in one year. In adolescent fish, fullness started gradually to increase from Sep. to Dec. with condition factor ranged from 2.451 to 2.852, and decrease gradually from next January to Apr. with ACF ranged from 2. 693 - 2. 306, and remained roughly the same with 2. 337 - 2. 365 ACF from May to Aug. In adult fish, fullness with 1. 775 - 2. 894 ACF varied obviously with season from July to Dec. Algae was possibly an important food item in the gut contents with a frequency of occurrence of 100% and average wet weight of 25.0% plus in the life history of the Down-spine Carp, S. denticulatus.