Yellowhead Jawfish Hatching Eggs

Yellowhead Jawfish Hatching Eggs: A male jawfish releases hatching eggs.

Bonaire, 2009 – Hatching jawfish eggs! A male jawfish has guarded these eggs in his mouth for close to a week, and we managed to photograph and video them hatching. It only took fifteen years to get the shot!  We fell in love with jawfish in 1995 in Bimini. The first magazine article that Ned and I wrote together for Ocean Realm magazine was about Yellowhead Jawfish, Opistognathus aurifrons (a link to a scanned copy of the 1995 article is at the end of this post).

When we decided to write our Reef Fish Behavior book, we devoted many dives to observing jawfish behavior. We captured images of jawfish courting, jawfish fighting, jawfish building burrows, male jawfish guarding eggs – but no hatching. After we published the first edition of the book in 1999, we moved on to other projects. We finally decided to try again in 2009, during our annual stay in Bonaire.

Males exercise an extreme form of parental care by holding bundles of fertilized eggs in their mouths, occasionally partially spitting them out and quickly sucking them back in to aerate the mass of developing embryos (a behavior known as churning). They guard their broods for up to a week but we were never able to catch one in the act of releasing hatching eggs. Early on we saw a photo of a Pacific species and were told it happened just before sunrise, and were later told that it was the same for the Caribbean species. This bit of misinformation got us out of our bed at 5 AM to make several unsuccessful pre-dawn dives. 

A male jawfish aerates eggs that he is guarding in his mouth.

At the beginning or our 2009 Bonaire stay, Ned called our friend Ellen Muller to ask if she could offer any clues. “Thirty minutes after sunset,” was her reply. This was at the beginning of a five-week stay, so we had plenty of time to stake out jawfish. We found colonies in front of Buddy Dive, and at several additional popular dive sites up and down the coast. Basically any sandy shelf along the edge of reefs that we dived, had Yellowhead Jawfish. 

We searched for males with bulging jaws – something that can be seen from a distance once we developed a proper search image. Males guarding eggs seem to be more wary than normal, and if spooked into their holes, can take quite a while before reappearing. Once we discovered a male with eggs, we crept closer to check out the eggs’ color. If yellow, i.e., full of fresh yolk, we figured we had a few days to wait for further development. When a mass of embryos turned dark silver, indicating enlarging eye pigment, hatching became imminent. We marked the spot with loose pieces of rubble to guide our return just before dusk. 

On any given day, we identified several potential targets with well-developed silver egg bundles, but of course they were located at different dive sites up and down the coast. So we would make a guess, picking an individual with the darkest eggs or one we’d been monitoring the longest, and from dusk to well after dark, lay in wait for a hatching. Ten days later, still no luck.

I was not with Ned the evening he finally got the shot. Instead I was sitting in the Buddy Dive traffic circle with friends, waiting for him to return from what was supposed to be a quick check on a jawfish before we all headed out for a night dive at Salt Pier. Thirty minutes late, Ned rolled up, popped out of the truck cab with a Cheshire cat grin, and did a jig. I spent the Salt Pier dive shaking off the annoyance that I missed the long-awaited event. 

Back at the room, Ned explained that he really didn’t expect success until he shined his light down the burrow opening and found the jawfish wedged inside, just below the entranceway. A light bulb went on. We already knew that prior to bedding down for the night jawfish routinely pull a rock or other piece of debris over their holes for protection. While all the other jawfish in the little colony had already capped their holes for the night, Ned deduced that the male he was observing hadn’t covered his hole because he might be ready to release his mouthful of hatchlings! Ned felt certain this was the night, but each time he snapped on his strobe’s modeling light, the male retreated deeper underground. We don’t use red lights – much marine life isn’t bothered by red light – but one might have come in handy this time. He prefocused his camera (he shoots all manual) then held his camera away so the modeling light filtered through his fingers, barely lighting the burrow entrance. With less light, the jawfish emerged within minutes and began huffing and puffing, releasing batch after batch of freshly hatched larvae with each jerk of his head. Once the eggs started hatching, the jawfish appeared to be committed and didn’t disappear down his hole even when Ned swung his camera and modeling light into position and started snapping frame after frame, timed with each release.

It was now my turn to get the video – easy now that we knew the key, right? Ned felt that jawfish would not come out with my video lights glaring. I was using a tripod, so once set up, repositioning would be difficult. I decided to try setting up the tripod, focusing on the burrow entrance, aiming the lights, then using my hands to dim them, much like Ned had done earlier. Even though I located several jawfish papas-to-be, it still took three weeks to capture the video.

Male jawfish are mouthbrooders, guarding eggs in their mouths until they hatch.

The first attempts were rather Keystone Cops-esque. We arrived at a marked fish, only to find that it had covered its hole for the night. In these cases we would rush out of the water, throw our gear into the truck, and quickly drive to the next site!  What had originally seemed like a sound strategy wasn’t working. I finally found what I believed to the perfect jawfish on Buddy’s Reef, at 20 feet. Unfortunately, it was where divers began their shore dives, and every time they swam over where I was kneeling on the sand, my already nervous subject disappeared deep inside its burrow for 10 minutes or so. Two and a half hours later, low on air and camera battery, I swam back to shore. When I checked on the fish the following morning, it was up in the water column above its burrow, eggless and merrily picking plankton.

There were other frustrating dives, at times disrupted by nosy Tarpon, opportunistic soapfishes, and foraging Sharptail Eels. I confess to swatting a Tarpon or two that swooped in too close, startling both me and the jawfish. Disgruntled by a wayward swat, one big Tarpon let out a percussive boom that nearly gave me heart failure, and sent the jawfish scrambling deep inside his burrow never to return. 

I was becoming even more antsy and a bit crazed when everything finally fell into place one night on the slope at Front Porch, just down the road from Buddy’s. The jawfish hadn’t covered its hole so I quickly positioned my video and let it roll with the lights aimed but turned off. Earlier attempts of screening the bright lights with my hands just hadn’t worked. Settling a body length away, I screened the beam of a weak spotting light through my fingers, barely illuminating the quarter-sized hole, and waited. Things weren’t quite as perfect as we’d hoped – a brisk current kept the lights and tripod wobbling. The instant I realized the jawfish was releasing his eggs, I switched on the video lights. To my relief, the jawfish continued to jerk his head, releasing wave after wave of tiny larvae. My woes weren’t over. The bright video lights attracted a swarm of demented silversides. At one point the infuriating finger-sized fish flew into the scene, sending the startled jawfish out of sight. Thankfully his translucent larvae kept coming, somersaulting out of the opening and disappearing into the night. One unfortunate silverside managed to knock itself silly on my housing, flopping weakly in the foreground (a little video editing took care of that) but the jawfish, committed to releasing its eggs, carried on.

We left Bonaire two days later with the images of a Yellowhead Jawfish hatching eggs we had been long seeking. They were later added to the jawfish chapter in the second edition of Reef Fish Behavior, published in October 2019. Ned wrote his account of getting the shot in “Bonaire: A Naturalist’s Dream”, published in the Winter 2010 issue of Alert Diver.  A pdf of our 1995 Ocean Realm article is here.