Ž .
Aquaculture 185 2000 339–352 www.elsevier.nlrlocateraqua-online
Identification of feeding stimulants for striped bass, Morone saxatilis
Elias Papatryphon, Joseph H. Soares Jr.
Graduate Program in Marine – Estuarine and EnÕironmental Sciences and Department of Animal and AÕian Sciences, UniÕersity of Maryland, College Park, MD, 20742-2311, USA
Received 9 August 1999; received in revised form 28 October 1999; accepted 29 October 1999
Abstract
A series of experiments were conducted to screen amino acids and other compounds, presented Ž
. Ž
individually or in mixtures, as feeding stimulants FS for striped bass. Two bioassays experiment .
series A and B were conducted. The FS carrier in series A was a nutritionally complete plant feedstuff-based diet whereas in series B, the basal was an agar-gel matrix. The second bioassay
proved to be the more sensitive testing and delivery system. Striped bass had a maximum response to the neutral amino acids, and particularly to
L
-alanine and
L
-serine. Inosine-5
X
-monophosphate and betaine were the only non-amino acid compounds that elicited a significant positive response.
All combinations tested of
L
-alanine,
L
-serine, inosine-5
X
-monophosphate and betaine stimulated feed intake for striped bass, the maximum response being attained when all four compounds were
included together in the feed. Additive andror synergistic effects between the compounds may have accounted for the enhanced response of the mixtures. q 2000 Elsevier Science B.V. All
rights reserved.
Keywords: Feeding; Stimulants; Striped bass; Palatability
1. Introduction
Striped bass is an important food fish in the US and is currently being cultured Ž
commercially for human consumption along with hybrid striped bass Harrell and
Corresponding author. Tel.: q1-301-405-5785; fax: q1-301-314-9059. Ž
. E-mail address: js89umail.umd.edu J.H. Soares Jr. .
0044-8486r00r - see front matter q 2000 Elsevier Science B.V. All rights reserved. Ž
. PII: S 0 0 4 4 - 8 4 8 6 9 9 0 0 3 4 7 - 6
. Webster, 1997 . Several nutritional studies have been conducted with striped bass and its
hybrids, particularly focusing on practical diet evaluations, nutrient requirements and nutrient availability. To our knowledge, there is only one published study on feeding
Ž .
Ž .
stimulants FS for striped bass Hughes, 1997 . The identification of FS is valuable both from a practical and a scientific standpoint. Previous research has demonstrated that
FS supplementation can enhance the acceptance of artificial feeds by larvae and fry ŽMeteiller et al., 1983; Person-Le Ruyet et al., 1983; Hughes, 1991; Kamstra and
. Ž
Heinsbroek, 1991 , increase the consumption of poorly palatable feeds Takeda and .
Ž . Ž
Takii, 1992 , increase feed consumption thus leading to higher growth rates Heinsbroek .
and Krueger, 1992 , and may be included in lures for commercial and recreational Ž
. fishing Jones, 1992 . Using FS to increase the palatability of formulated feeds for fish
can therefore result in an increase in total feed intake leading to a reduction of overall feeding time and subsequently feed wastage.
Compounds that have been associated with gustation in carnivorous fish are amino acids, nucleotides, quaternary ammonium compounds, organic acids and other low
Ž .
molecular weight components of animal tissues Carr et al., 1996 . Mixtures of FS have Ž
been reported to be more effective than individual compounds Takeda et al., 1984; Carr .
and Derby, 1986 . In addition, natural prey extracts, as well as their synthetic counter- parts, are very effective FS for a variety of fish species and have been used as references
in studies where the goal was to identify the simplest mixture or individual compounds Ž
that would yield a maximum feeding response Carr, 1976; Mackie et al., 1980; Ikeda et .
al., 1988; Fukuda et al., 1989 . Of great importance when screening for FS is the sensitivity and duration of the bioassays, especially when a large number of compounds
are to be tested. Although it is difficult to separate responses due to olfaction from those due to gustation in fish, it is believed that the final step in the feeding behavior, that of
Ž ingestion, is a response to the palatability of the food item and is gustatory based Marui
. and Caprio, 1992; Hara, 1994 . The purpose of this study was to identify the amino acid
Ž component responsible for the feeding stimulatory activity of a menhaden BreÕoortia
. tyrannus homogenate prepared in our laboratory; to evaluate the use of an agar-gel
carrier as a rapid and sensitive assay; to screen a number of compounds for FS activity; and to develop a simple yet effective FS mixture for striped bass.
2. Materials and methods
