Abstract

Sufficient feeding--an indispensable condition of marine mammals' successful maintenance in dolphinariums--should be based on formation of food allowance in view of energy needs of each particular animal. Implementation of this approach necessitates regular individualized quantity record keeping and quality balance control of the seafood, used for nourishment.

Theoretical computations of adequate fish quantities for marine animals, permitting definition of energetic requirements of specific individuals in the view of age, physiological state, and specificities of conditions of maintenance are rather labor-consuming and hardly applicable in real conditions of many dolphinariums^1,2.

The objective of the present study was to characterize the nutritional parameters of the diets used in Utrish Dolphinarium for feeding cetaceans, on the basis of the formalized approach to seafood's energetic value estimation. The research was performed in 2003-2007 on five female and two male Black Sea bottlenose dolphins (Tursiops truncatus ponticus), as well as one female and three male white whales (Delphinapterus leucas), kept in Sochi and Lazarevskoe branches of the enterprise, where individualized differentiated quantitative account of seafood fed to marine mammals is carried out on the regular basis.

The cetaceans' food allowances in Utrish Dolphinarium usually include 3-5 kinds of seafoods with various caloric values fed simultaneously. The rations consist of fish with different fat content: "average"--sprat, scad, rock trout, capelin, smelt, "fatty"--herring, humpback salmon, "lean"--walleye pollack, bakling, Arctic cod, and squid. Supplementation with vitamins ("Complivitum" as basis, plus addition of vitamins B₁, A, E, C and folic acid) is standard. The diets are individualized and depend upon the age, weight, physiological state and activity, intensity of trainings of the animal, season of the year, temperature of water in the pool, etc. The correction of rations are made according to the results of blood tests and body weight's dynamic.

The nutritional values of diets were calculated according a published simplified method,³ and the results were submitted in the form of conditional forage units (CFU) and specific daily norm of feeding (SDNF, calculated as CFU/10 kg animal's body weight). One kilogram of the "standard" fish--scad (with total energy--1310 kcal/kg; exchange energy--1130 kcal/kg; and following composition: 76.5 %--water, 4.5%--fat, 18.5 %--fibers, and 1.4 %--ash) was accepted as one CFU. The nutritional values of other seafoods (in CFU) were taken from published values³ on the basis of series applicable criterion method.

The average daily amounts of fed fish and indices of conditional nutritional value varied in the surveyed bottlenose dolphins between 8.4-8.6 kg (7.45-7.6 CFU) in summer and 7.6-8.7 kg (7.7-9.3 CFU) in winter. In the white whales these parameters fluctuated within 14.1-15.7 kg (13.6-15.5 CFU) in summer and 17.8-19.9 kg (19.8-21.1 CFU) in winter.

The values of SDNF obtained, varied within the limits of 0.35-0.42^CFU/_{10 kg} in summer and 0.44-0.49 ^CFU/_{10 kg} in winter for the bottlenose dolphins, and between 0.15-0.22 ^CFU/_{10 kg} in summer and 0.2-0.28 ^CFU/_{10 kg} in winter for the white whales.

Results of the current investigation are consistent with published data³. Positive individual dynamics of animals' body weights, as well as the findings of hematological and serum chemistry examinations, testify to the sufficiency of cetaceans' diets, utilized in Utrish Dolphinarium. The values of SDNF acquired in this study can be used as a reference guide for development of food allowances for bottlenose dolphins and white whales kept in the similar conditions.

We are inclined to think that the simplified approach to the estimation of seafood's nutritional value presented is convenient for practical use and quick correction of marine mammals' diets. It is especially important currently, when the choice of fish for feeding animals often depends on availability for purchase.

References

1.  Worthy GAJ. 1990. Nutritional Energetic for Marine Mammals; Addendums.

2.  In: Dierauf LA, ed. CRC Handbook of Marine Mammal Medicine: Health, Disease and Rehabilitation. Boca Raton. Pp. 489-520.

3.  Worthy GAJ. 2001. Nutrition and Energetics. In: Dierauf LA and Gulland FMD, eds. CRC Handbook of Marine Mammal Medicine. Second Edition. Boca Raton. Pp. 791-827.

4.  Zhurid BA, Verizhnikova SA. 2000. Feeding of marine mammals in an oceanarium. Sevastopol: "Aquamarine", 368p (in Russian)