Spawning and Rearing the Sonora Goby, Gobiosoma chiquita Part 1
Species Characteristics, Natural History, and Spawning Conditions
It probably won’t win any beauty contests. A starring role in a feature film seems unlikely. And yet, a humble, almost universally overlooked species of goby was selected to provide a memorable experience to a group of high-school marine biology students. As part of a semester-long project, students were successful in their attempt to breed and rear an intertidal goby from the Sea of Cortez. This was a species of goby that had not previously been reported as having been successfully reared through its entire life cycle in captivity. Their processes, observations, and the results of experimentation with alternative feeds, microbial microflora, and water chemistry are described in this three part series. It is hoped that others who wish to try rearing marine fishes on a small scale might be able to adapt these techniques for their own endeavors, and that educators may find ideas on how to bring the field of marine aquaculture into the classroom.
The goby that was selected for the project was the Sonora Goby, Gobiosoma chiquita, which is also sometimes referred to as the blushing goby, due to the pinkish hue that the gills impart to the cheeks through a thin semi-transparent operculum. This goby is endemic to the Northern Sea of Cortez where it lives in the turbulent waters of the intertidal zone. This habitat preference was one of the deciding factors in the selection of this fish for a classroom-rearing project. A fish that can survive an environment where afternoon water temperatures can rise to nearly 38 degrees Celsius (100 F) in the summer, and drop to below 10 degrees Celsius (50 F) in the winter, with variations of over 20 degrees in a 12-hour period, seemed a likely candidate to survive a High School classroom. In addition to their hardiness, another factor in their selection was that other members of the genus Gobiosoma have been bred with relative ease in captivity, most notably the neon goby, Gobiosoma oceanops, (now Elactinus oceanops, but closely related nonetheless), which was one of the first marine ornamentals bred in captivity in the 1970’s.
As a part of this rearing project, students also took the opportunity to experiment with a variety of rearing methods such as the utilization of cryopreserved algae paste as a substitute for live microalgae in rotifer culture. During a rotifer shortage the use of micronized foods as a rotifer substitute was explored. Microbe populations and chemical parameters were tracked in the various rearing tanks and became the basis for two award-winning science fair projects.
The Sonora Goby is a small fish, which rarely exceeds 2 inches standard length. Sexual dimorphism is not readily apparent, although adult males tend to be slightly longer and slimmer than the females, which will have a visibly distended abdomen when ripe with eggs. Coloration varies from light beige to a deep olive drab depending on the color of the substrate. Males will turn very dark, nearly black when tending a nest of eggs.
Although these fish lack the bright colors that many reefkeepers desire, they nonetheless have many fine attributes that make them worthy of an aquarist’s consideration. They are active diurnal feeders that will vigorously clean every nook and cranny of an aquarium. Although they will happily perch themselves on leather corals and mushroom anemones, they have not been observed harassing any invertebrates except for flatworms and copepods, which they consume with zeal. They will greedily accept nearly any frozen, live, or flake food. They are docile towards other fish and can be kept in groups with only minimal squabbling amongst themselves over who gets to sit on which rock. Most of all they have personality and will quickly recognize their keepers as the bringers of food and will assume a begging behavior as soon as keepers approach their tank. Because of their extreme hardiness and value as a reef cleaner, they could be an ideal starter fish, tough as a damsel, without the eventual attitude. As the tank and reefkeeper mature, they will continue to earn their keep by keeping the sand and rocks free of detritus and uneaten food.
Spawning the Sonora Goby
For this breeding project, 3 sub-adult Gobiosoma chiquita were collected during a University of Arizona trip to Puerto Penasco in Sonora, Mexico where they are especially abundant. They live along the sand-rock interface in the many pools left by the tremendous tidal range that is present in the region. These individuals were collected in mid-November and were placed in a 20-gallon soft coral culture tank. This tank contained a single adult Gobiosoma chiquita, which had been introduced 6 months previously from a prior sampling trip. The temperature was maintained at 23-24.5 degrees Celsius (73.5-76°F). Cooler waters were selected because the Neon Goby reportedly spawns more readily in wintertime. Reef Fishes of the Sea of Cortez, the bible for ichthyologists working in the Gulf of California, reports the breeding season for Sonora Gobies begins in spring when temperatures are cool, and continues throughout the summer. Instant Ocean artificial seawater was used to maintain salinity at 35ppt with 5% weekly water exchanges. Filtration was provided by approximately15 lbs. of live rock, over 4 inches of aragonite flooring. Additional water circulation was provided by a power-filter with the media replaced by rubble. No supplements were found to be necessary to maintain the health of either the fish or invertebrates in this tank. Lighting was provided by a 55-watt 50/50 power-compact light-strip, 4 inches over the tank, with a 12-hour photoperiod.
In mid December, approximately one month after introduction, the first spawning occurred. Spawning occurred in late afternoon when a swollen female was observed entering the nest area that the larger, older individual had claimed under a halved bivalve shell. A clutch of about 100 small, white, opaque eggs with a slight orange tint were deposited on the ceiling of the shell cavity. Spawning events with this first female were repeated every 12-14 days thereafter. Although spawning occurred only every two weeks or so, eggs of varying states of development were often seen simultaneously in the same spawning site. Close observation revealed that the gobies had entered into a haremic situation in which all 3 of the younger gobies functioned as females, breeding with a single older male. This situation may indicate that Gobiosoma chiquita is capable of protogynous hermaphrodism in which the largest member of a community becomes a male, while less dominant fish remain in a female state until the dominant male is removed from the group. However, the situation observed in this aquarium does not necessarily rule out the possibility of separate and fixed sexes, it may have just been the luck of the draw that we happened to catch 3 females on this trip and a male on an earlier trip. Further experimentation on the progeny of these original adults will hopefully answer this question with greater certainty.
In subsequent sections, we will look at the larval rearing process for this species. Included will be a look at the use of various methodologies such as greenwater technique, the use of cryopreserved algal pastes, and alternative larval feeds. The effects of these various strategies will be examined as they relate to chemical water quality parameters, microbe populations, especially pathogens from the genus Vibrio, and most important, larval survival and metamorphosis.