It seems only fitting that our first creature feature focuses on one of the first marine ornamentals to have been raised successfully in captivity, the Neon Goby, Elacatinus oceanops, (formerly Gobiosoma oceanops). First reared in the 1970’s the neon goby is a popular aquarium fish owing to its general hardiness, attractive appearance, and abilities in picking ectoparasites off of other fishes.

Size and Appearance

Neon gobies are small and typical gobiioid in shape. Most Elacatinus spp. are less than 5cm (2 inches) total length. Neon gobies are black overall with a neon blue stripe extending from front of eye to the base of caudal fin.

Broodstock Care

Omnivorous and hardy they will do well in nearly any species-only or reef aquarium situation, but due to their size should not be kept with larger predatory fishes. Neon gobies do best in water temperatures below 26.5 decrees C (80 degrees F). Foods should include a variety of grated frozen shrimp, squid and fish, as well as commercial gelatin or pellet diets. Multiple feedings daily will condition neon gobies for spawning.

Pair Formation

Hermaphroditic sexual patterns are common in the family Gobiidae. I am not aware of a definitive classification of Elacatinus oceanops, but experience in our lab suggests that they are sequential hermaphrodites rather than simultaneous hermaphrodites.
Males are often larger and more slender. Females will possess a swollen abdomen, particularly when ripe with eggs.

Neon Gobies may be kept as groups of 6 or more individuals when provided with sufficient hiding spots, as these gobies can be quite quarrelsome. If they are to be kept as a pair, they should be observed closely during the first week after introduction. If fighting is excessive, one member of the pair should be swapped until marital harmony ensues. Groups of fewer than 6 individuals are not suggested, as pairs will begin to try to “evict” other gobies in their territory. Larger groups dampen and disperse these aggressive tendencies.

Spawning and Hatching

Spawning can occur as often as every fourteen days with plenty of feeding and warm water conditions. In their natural environment, demersal eggs are laid in small holes and crevices in the reef and under discarded bivalve shells. In captivity, small Tridacna sp shells serve well, as do halved clay flowerpots and short sections of half inch PVC pipe. Both parents tend eggs. Depending on temperature, hatching will commence in 6-8 days. Hatching occurs after dark.

Larval Rearing

Neon goby larvae are slightly shorter and substantially slimmer than clownfish larvae. The larval period ranges from 18-25 days depending on temperature and food type. The first diet is rotifers, followed by Artemia nauplii. The transition period is variable between these foods. Elacatinus larvae can be transitioned to Artemia as early as day 6, and while growth is more rapid, mortality is often high. Waiting until day 12-15 to begin Artemia feedings will delay metamorphosis by a few days, but will also significantly increase survivorship. We have successfully reared batches of neon goby hatchlings through metamorphosis only on rotifers, but metamorphosis took 30-35 days.

Spawning and Rearing the Sonora Goby, Gobiosoma chiquita: Part 2

Larval Hatching and Development

In Section One, we looked at the species characteristics and spawning behaviors of a tough little goby from the Sea of Cortez, the Sonora Goby, Gobiosoma chiquita. In this section we will look at the larval development of this fish and begin to describe the methodologies used in rearing the larvae through to metamorphosis. Subsequent articles will delve into the use of alternative feeds such as frozen microalgae and dry artemia and rotifer substitutes, particularly as this relates to water quality, larval survival and growth, and microbial populations.

Egg Development and Larval Hatching

Hatching occurred on the 9th evening after egg deposition. During development, the eggs turned from a milky opaque to a transparent membrane, which surrounded an easily-visible larvae. Silvery eyes became apparent 1-2 days before hatch. The first hatch was allowed to occur naturally and began 2 hours after the lights went out. All larvae were hatched within 20 minutes, no doubt due in part to the vigorous fanning provided by the male immediately before hatch began. This first hatch was siphoned through a 3/8” piece of silicone tubing into a 10-gallon larval tank. Subsequent larval collection was made much easier with the discovery that hatching could be induced anytime in the afternoon that hatching was scheduled. By exposing the eggs to bright light, (2- 40 watt fluorescents, 1 foot away) and swishing the nest back and forth in water for about 10 seconds, the larvae would begin to hatch within a few minutes of treatment when placed into a suitably dark rearing tank. Using this technique, it was possible to hatch the nests remotely in the larval rearing tanks and avoid the tedium and trauma of trying to catch all of the larvae in the parental tanks. Although the male goes into a frenzy when his nest is removed, when it is replaced 30 minutes later, he immediately calms and resumes his nest tending duties without hesitation. In one case both the male and an overly anxious female swam into the shell and began to spawn in mid-water as the shell was lowered back to the bottom of the tank.

Early Larval Rearing

There is only one word to describe the larvae of Gobiosoma chiquita-Hardy! Within moments of hatch and siphoning, the first larvae were already feeding aggressively on rotifers. Sonora Goby hatchlings are 2-3 mm long with slender bodies and protruding silver eyes. They are not nearly as robust as clownfish, instead more closely resemble the larvae associated with the pseudochromids. They are immediately active and hungry after hatch, taking rotifers with much more skill and accuracy than a clownfish of comparable age. Most bellies can be seen turning silver and bulging with the newly consumed rotifers only 10 minutes after hatch.

For these rearing experiments, several variants of the greenwater technique were utilized. Relatively low densities of larvae (10-20/gallon) were maintained with 10-15 rotifers/ml and either live or frozen microalgae was added directly to the rearing tanks to keep the rotifers enriched and reproducing. There were several advantages to this form of larval rearing in a classroom environment. First, by having a continuously reproducing colony of rotifers in the tank, there is less worry of insufficient prey items in the tank for the larvae to consume. This became especially important on the weekends when 4 or more harvests of rotifers each day would be inconvenient to say the least. Using this technique, simply adding algae once in the morning assured that a supply of nutritious rotifers would be available for the larvae all day. In addition to the advantage of continuous food supply, utilization of live microalgae also serves as a water conditioner to some extent, utilizing the wastes of the larvae and rotifers for their own metabolism.

Because the exact nutritional requirements for this species were unknown, a variety of microalgae species were utilized as rotifer food in order to provide HUFA and EPA profiles that were as diverse as possible. The hatches were split between two tanks so a variety of rearing methods could be tried for each group. Live Tetraselmis and Nanochloropsis were added at least once per day in one tank, which received only live microalgae. In a separate tank, only frozen Isochrysis, Tetraselmis, and Nanochloropsis species from Reed Mariculture were regularly added, as was a small dose of astaxanthin, a pigment believed to aid in oxygen transport and increase survival in clownfish larvae.

Our next section will cover the effects of these various rearing methods on factors such as water chemistry, bacterial levels, and most important, larval growth and survival.

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.

Species Characteristics

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.