Fish production and related limnology in two experimental ponds as influenced by fertilization

Graduation date: 1967The merits of fertilizing warmwater fish ponds with dry organic manure were studied from October, 1964 to November, 1965 using two experimental ponds in the Willamette Valley. One pond (pond II) was fertilized with urea and single superphosphate and the other (pond III) was fertilized with dried manure as well as with urea and single superphosphate. A study of the important environmental variables and the growth and production of largemouth black bass, Micropterus salmoides (Lacepede), was employed in an attempt to test the effects of fertilization with manure.\ud The addition of manure to pond III failed to produce any striking effects in the physical and chemical characteristics in the pond; however, some reduction in the dissolved oxygen content of the bottom water of pond III, as compared with pond II, was noted. Nearly equal biomasses of limnetic microcrustaceans were observed in the ponds during the course of the experiment. The added manure first appeared to stimulate the abundance and weights of chironomid larvae and pupae and then depress them. Numbers and biomasses of these insects in pond III were more than double those of pond II during the early portion of the experiment. After the spring emergence periods they became greatly reduced in pond III as compared with pond II. The mean weights of the three size classes of largemouth bass in pond II were greater at every sampling period compared\ud with the corresponding size classes in pond III. The survival of adult bass was higher in pond II than that of pond III. The differences in growth and mortality of bass between the two ponds was\ud thought to be due to the reduction in chironomids in pond III in the latter portion of the experiment and the larger populations of the rough-skinned newt, Taricha granulosa granulosa (possible competitor with bass) in pond III. The addition of steer manure to pond III appeared to be of little value in respect to bass production. The production of bass on an acreage basis was more than doubled in pond II over that of pond III, leading to the rejection of the hypothesis that addition of organic matter in the form of dry composted steer manure would increase the production of largemouth bass