First-year growth of longnose gar (Lepisosteus osseus) from zygote to autumn juvenile.
Absolute growth of longnose gars has never been measured from a known date of fertilization of an ovum in the wild to near the end of the first growing season over a precisely known number of days of life. Riggs and Moore (1960) reported that five young-of-the-year long-nose gars collected from Lake Texoma and held in aquaria for 25 days in July and August grew in total length from ca. 250-300 mm to 300-370 mm, with average growth of 3.2 mm/day. Netsch and Witt (1962) tracked growth of 20 young-of-the-year longnose gars taken from streams in Missouri and held in wash tubs for 52 days from July to September; they started with individuals initially averaging 135.7 mm total length. They reported an average growth of 2.5 mm/day during that period. Echelle and Riggs (1972) reported estimated dates of spawning from sizes of wild-caught longnose gars in Lake Texoma, as part of a study of life history, finding them to be 207-306 mm total length by late summer (23 August-1 September). Carlander (1969) collated statistics for growth from published and unpublished sources, and Simon and Wallus (1990) summarized details of reproductive biology from published information. For this species, Simon and Wallus (1990) indicated that growth was variable but rapid and that there was <513 mm total length in the first year. Trautman (1981) reported young of-the-year in Ohio were 254-381 mm total length by October. Thus, the longnose gar whose growth we report herein is within the size ranges noted by Trautman (1981) or other authors previously, so we suggest that its growth, although in a small fish pond, was about that of this species in streams or lakes.
[FIGURE 1 OMITTED]
On 18 May 2010, longnose gars were observed throughout the afternoon to be engaged in vigorous spawning activities in a rocky shoreline on the north side of Lake Texoma at the University of Oklahoma Biological Station, Marshall County, Oklahoma; 33.88[degree]N, 96.80[degree]W. Several large females, up to ca. 1 m total length, continually swam alongside large rocks in shallow water at the shoreline, accompanied by as many as 4-5 smaller males (Fig.1). Fertilized eggs were abundant, adhering to rocks in shallow water. At ca. 1700 h, we placed several of these eggs into a cup of lake water and held them overnight indoors at room temperature. The next day we transported them to Norman, Oklahoma, where we placed them in a fish bowl with mild aeration until they hatched on 22-23 May. The yolk-sac larvae typically maintained their position by attachment with their rostral adhesive organ. Subsequently, we transferred two 5-dayold larvae ca. 10-12 mm total length to an outdoor ornamental pond within the city of Norman. Two others that we kept in an aquarium began feeding on zooplankton over the next few days. The oval pond was ca. 200 cm long, 140 cm wide, and 25 cm deep, lined with inert, black, pond liner. it was aerated gently with a small pond pump and exposed to about one-half day of sun underneath silver maple (Acer saccharinum) and sweetgum (Liquidambar styraciflua) trees, which provided inputs of leaf litter and small woody debris. The pond was given only minimal disturbance throughout summer and water remained generally murky, limiting our ability to make direct observations. Numerous western mosquitofish (Gambusia affinis) were also in the pond, and apparently reproductive, as we commonly observed neonate Gambusia all summer at edges of the pond.
We did not see either of the two small gars again until, when starting to drain the pond, we found that one had survived, apparently in good condition, and had reached a large size. On 31 October 2010, we gently netted it from the pond, photographed it alongside a metal tape measure in the net, and transferred it to an insulated container. We then transported it to a different, much larger ornamental pond, where it was released unharmed.
The individual gar had grown since May, unmolested and unobserved, in a pool providing a semi-natural outdoor environment. The pond was open to fly-in insects, deposition of eggs by insects, or both, e.g., chironomids and small neonate Gambusia were abundant. Riggs and Moore (1960) reported that young-of-the-year longnose gars readily ate small fishes, and Netsch and Witt (1962) fed captive young-of-the-year gars live minnows in their experiment. Echelle (1968) and Echelle and Riggs (1972) identified Gambusia as a normal component of the diet of juvenile longnose gars in Lake Texoma. Thus, we assume that the gar in our pond had an adequate supply of various foods. Growth of this individual (1.57 mm/day) was below ranges reported by Moore and Riggs (1960; 2.3-4.5 mm/ day) and Netsch and Witt (1962; 2.5-3.4 mm/day). This probably reflects differences in growing conditions (seminatural versus a more controlled laboratory environment), interval of time (166 versus 25 and 52 days), and number of life stages (zygote to large juvenile versus juvenile only) over which growth was measured. Our observations started in late spring (cooler temperatures) and continued into autumn when temperatures were decreasing and growth may have slowed. Mean air temperatures ( [degrees]C) during the time our gar was held in the ornamental pond were: June, 27.3; July, 28.1; August, 29.5; September, 24.4; and October, 17.3. Because survival of the gar was unknown until late October, we had no interim measurement to estimate a growth curve over shorter periods. However, total growth of this individual, from fertilized egg to large juvenile, over most of a growing season, provides a likely estimate for rates of growth of young longnose gars across the range of weather conditions from hatching to onset of cool autumn temperatures at the latitude of central Oklahoma.
We thank C. Vaughn for the photograph of spawning gars in Lake Texoma, A. T. Marsh and A. Hiott for assistance with recovery of the gar, and D. Donoso for the Spanish translation.
CARLANDER, K. D. 1969. Handbook of freshwater fishery biology. Volume 1. Iowa State university Press, Ames.
ECHELLE, A. A. 1968. Food habits of young-of-year longnose gar in Lake Texoma, Oklahoma. Southwestern Naturalist 13:4550.
ECHELLE, A. A., and C. D. Riggs. 1972. Aspects of the early life history of gars (Lepisosteus) in Lake Texoma. Transactions of the American Fisheries Society 111:106-112.
NETSCH,N. F., AND A. WITT, JR. 1962. Contributions to the life history of the longnose gar (Lepisosteus osseus) in Missouri. Transactions of the American Fisheries Society 91:251-262. Riggs, C. D., and G. A. Moore. 1960. Growth of young gar (Lepisosteus) in aquaria. Proceedings of the Oklahoma Academy of Science 40:44-46.
SIMON,T. P., AND R. WALLUS. 1990. Family Lepiosteidae. Pages 5785 in Reproductive biology and early life history of fishes in the Ohio River drainage. Volume 1, Acipenseridae through Esocidae (R. Wallus, T. P. Simon, and B. L. Yeager, editors). Tennessee Valley Authority, Chattanooga, Tennessee.
TRAUTMAN, M. B. 1981. The fishes of Ohio. Second edition. Ohio State university Press, Columbus.
Submitted 4 February 2011. Accepted 21 February 2012. Associate Editor was Robert J. Edwards.
William J. Matthews, * William L. Shelton, and Edie Marsh-Matthews
Department of Biology, University of Oklahoma, Norman, OK 73019 (WJM, WLS, EMM)
Sam Noble Oklahoma Museum of Natural History, Norman, OK 73072 (EMM)
* Correspondent: email@example.com
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|Author:||Matthews, William J.; Shelton, William L.; Marsh-Matthews, Edie|
|Date:||Sep 1, 2012|
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