Reporting fish growth: A review of the basics

Kevin D. Hopkins, College of Agriculture, University of Hawaii at Hilo, Hilo, Hawaii 96720, USA

Abstract Aquaculturists typically report growth using absolute (g/d), relative (% increase in body weight), and specific growth rates (%/d). Less frequently, von Bertalanffy Growth Functions (VBGF) are used. Each of these rates is a numerical representation of growth which assumes a specific relationship between size and time (linear, exponential, or asymptotic). Aquaculturists typically determine size at time throughout their experiments. Unfortunately, the intermediate data points are usually ignored when computing growth rates (except for VBGF) and the appropriateness of the method for calculating growth for a particular data set is not tested. This paper reviews the basis and computation of each of the growth rates in an effort to encourage aquaculturists to use the appropriate growth rates.

This abstract was excerpted from the original paper, which was published in Journal of the World Aquaculture Society 23:173-179, 1992.

A research methodology for integrated agriculture-aquaculture farming systems

K.D. Hopkins, University of Hawaii at Hilo, Hilo, Hawaii 96720, USA

J.D. Bowman, Oregon State University, Corvallis, Oregon 97331, USA

Abstract A ten-step methodology for research on integrated agriculture-aquaculture farming systems is described. Particular attention is given to the interactions between the agriculture and aquaculture components. References to appropriate "standard" agriculture and aquaculture research methods are made.

This abstract was excerpted from the original paper, which was published as pages 89-98 in Techniques for Modern Aquaculture, Proceedings of an Aquacultural Engineering Conference, American Society of Agricultral Engineers, St. Joseph, Michigan, USA.

Supplemental feeding of tilapia in fertilized ponds

James S. Diana, School of Natural Resources and Environment, University of Michigan, Ann Arbor, Michigan 48109-1115, USA

Kitjar Jaiyen, Department of Fisheries, Ministry of Agriculture and Cooperatives, Kasetsart University Campus, Bangken, Bangkok 10900, Thailand

C. Kwei Lin, Asian Institute of Technology, G.P.O. Box 2754, Bangkok 10501, Thailand

1 December 1994 , CRSP Research Report 94-73

Abstract The addition of feed to fertilized fish ponds was evaluated by adding feed alone, feed plus fertilizer, or fertilizer alone to nine ponds stocked with Nile tilapia (Oreochromis niloticus). Two experiments were conducted. The first had 500 fish per 250 m² pond in 3-treatments: ad-libitum feeding; fertilizer only; or fertilizer and ad- libitum feeding. The second experiment had 5 treatments with 750 fish per pond: ad-libitum feed only; fertilizer only; or 0.25, 0.50, and 0.75 satiation ration plus fertilizer. Ponds in Thailand were maintained for 155- 162 d, during which chemical and physical properties were monitored. In experiment 1 tilapia growth was highest in feed only ponds, and lowest in fertilizer only ponds. Net yield did not differ significantly among treatments, due to variation in survival. In experiment 2, tilapia growth was lowest in fertilizer only ponds, intermediate in 0.25 ration ponds, and highest in 0.50, 0.75, and ad-libitum ponds. The latter treatments were not significantly different. Multiple regressions for each experiment indicated only 47-87% of the variance in growth was explained by feed and fertilizer input, while 52-89% of the variance in yield was explained by those factors. For both experiments combined, 90.3% of the variance in growth was explained by feed input, fertilizer input, alkalinity, and total inorganic nitrogen concentration. For yield, R² was 0.888 and the regression included feed input, pH, and number of low dissolved oxygen events. Experiment 1 appeared to approach carrying capacity near the end, while no reduction in growth occurred in experiment 2 at higher fish density and biomass. Reductions in growth in experiment 1 were not correlated with declining water quality late in the grow out. Combinations of feed and fertilizer were most efficient in growing tilapia to large size (500 g) compared to complete feeding or fertilizing alone.

This abstract was excerpted from the original paper, which was published in Journal of the World Aquaculture Society 25:497-506,1994.

Pond history as a source of error in fish culture experiments: A quantitative assessment using covariate analysis

Christopher F. Knud-Hansen, Department of Fisheries and Wilflife, Michigan State University, East Lansing, Michigan, USA, and, Division of Agriculture and Food Engineering, Asian Institute of Technology, G.P.O. Box 2754, Bangkok 10501, Thailand

1 December 1994, CRSP Research Report 94-74

Abstract Nine successive 5-month experiments, which examined relationships between fertilization strategies (with chicken manure, triple superphosphate and urea), water quality and yields of Nile tilipia (Oreochromis niloticus ), took place from February 1985 through March 1990 in 16 earthen ponds at the Ayutthaya Freshwater Fisheries Center, Bang Sai, Thailand. Over the course of these experiments, randomization of treatments resulted in all ponds having different fertilization histories. Analysis of covariance was used to quantify the carry-over effects of nutrient inputs from earlier experiments on experimental errors in Experiment 9.

Analyses of variance indicated that the residual (experimental error) accounted for approximately 39% of the total variation of net fish yield (NFY) observed in Experiment 9. Covariate analysis revealed that residuals were most significantly correlated to accumulated chicken manure input from Experiments 5 through 8. Previous pond fertilizations accounted for approximately 49% of total experimental variation in NFY observed in Experiment 9. Multiple linear regression analysis, using treatment inputs and the pond history covariate as the two independent variables to explain NFY, gave an r² = 0.75 (P < 0.001). Pond sediment chemistry data proved to be ineffective as covariates for reducing experimental error and/or predicting NFY.

Reasons for the positive effect of earlier experiments on NFY most likely involved the inverse relationship between the ability of pond sediments to remove soluble phosphorus from overlying water, and the accumulation of organic matter and phosphorus on pond bottoms. Pond management considerations and recommendations for fish culture experiments are given to better account for between-pond variability due to different fertilization histories.

This abstract was excerpted from the original paper, which was published in Aquaculture 105:21-36, 1992.

Growth of control and androgen- treated Nile tilapia, Oreochromis niloticus (L.), during treatment, nursery and grow-out phases in tropical fish ponds

Bartholomew Green and David Teichert-Coddington, Department of Fisheries and Allied Aquaculture and, Alabama Agricultural Experiment Station, Auburn University, Alabama 36849, USA

1 December 1994, CRSP Research Report 94-75

Abstract Masculinization of sexually undifferentiated tilapia fry is achieved by oral administration of the androgen 17-a methyltestosterone (MT). An anabolic response to androgen treatment of tilapia has been reported. Growth of control and MT-treated tilapia was evaluated during consecutive treatment, nursery, and grow-out phases under conditions approximating commercial, semi-intensive tilapia farms in Central America. Oreochromis niloticus (L.) fry were fed a 0 or 60 mg/kg MT diet for 28 days. Growth curves for control and MT-treated fish did not have significantly different slopes. Mean harvest fry weights were similar, averaging 0.1 g/fry for both treatments. Fry were subsequently stocked into 0.2-ha nursery ponds for 94 days growth. Slopes of control and MT-treated fish growth curves were not significantly different. Mean final individual weights did not differ significantly between treatments. Control fish did not deviate significantly from the 1:1 male:female ratio, but MT-treated fish were 97% males. Control male and MT-treated male fingerlings were stocked for grow-out into 0.1-ha organically fertilized earthen ponds. No significant difference in growth was observed between control and MT-treated fish. Mean gross yields after 150 days and mean final individual weights were similar for both treatments.

This abstract was excerpted from the original paper, which was published in Aquaculture and Fisheries Management 25:613-621, 1994.