Fish Pond Research Summer 2024- Fish Richness and Butterfly and Damsel Fish Size
Authors- Sierra Nunis, Taylor English, and Ryan del Rosario
Introduction
Our project was focused on recording the species richness in a transitional fish pond in Pa'eam Tahiti. Species or taxonomic richness is defined as the amount of different species in an area. Our sampling universe was the area encompassing the fishpond from shore to the furthest wall, as well as two areas 15 meters adjacent to the pond. We specifically decided to expand on a previous years research on species diversity, with our focus on the specific sizes of two target families: the butterflyfish and damselfish. Our aim is to compare the abundance of juvenile butterfly and damsel fishes inside the fish pond compared to areas outside, which could indicate how effective the pond is as a nursery, the recruitment rate, or the fitness of individuals that use the pond for shelter.
Methods
We used the same methods as the prior group as follows. We separated into two phases; monitoring the inside of the fish pond (including a special survey of the central rock formation), and then monitoring the outer rock walls and a transect 15 meters longshore from the outer walls to provide comparisons. The first swimmer did one pass to record the species richness three meters away from the transect to make sure to not disturb the fish. They then waited 2 minutes at the end of the transect to allow fish to return before swimming back over the transect to make additional records. After a minimum of 2 minutes, we would repeat the same methods but would instead record the abundance of juvenile and adult target families of butterfly and damselfish. Juveniles were calculated as being under a designated range. We classified butterfly juveniles as 4 cm or under and Damsel juveniles were 3 cm or under. This was repeated by two researchers with a total of four complete laps. The same methods were repeated for the other two transects surrounding the inside of the fish pond,as well as the exterior and 15 m away.
In relation to the prior groups we decided to change the methods to surveying the inner fish pond. In past years they designated a researcher to swim for 10 minutes around the exterior and then 10 minutes observing the interior. We believe being inside the small interior would frighten the fish so we just surveyed the exterior. When surveying the exterior we concluded that the swimming around the exterior would scare fish so we decided to have one researcher stationary about ½ a meter away to record any fish richness and size of damsel/butterfly for a total of 10 minutes. To best estimate the size, a small rock prior to entering the water was measured out to be approximately 3 cm and was placed on the rock structure to precisely know if the fish is within our juvenile range when swimming past it. This was a total of 10 minutes of patrolling and made exact by an underwater watch.
We did further research on the direct outside of the right and left walls of the fish pond. We did this by using the same methods as the inside rather just a meter from the edge going to the outer lagoonside. We also conducted two further transects 15 meters away from the center of each right and left wall. These transects were also going 15 m crossshore and the same methods were used.
Results
When looking at our graph, the x-axis indicated the areas surveyed, the bars indicate the classification of fish including their family and estimated age (of juvenile or adult), and the y-axis is number of individuals of each observed in their respective sampling universe. The adult damsel fish were the most observed, followed by adult butterfly, then juvenile damsel, and the least observed being juvenile Butterfly.The only location where neither were seen was the far right transect. The main locations for the juveniles were most abundant in the inner fish pond but juvenile damsel were seen in all but the far right, and juvenile butterfly were only observed in the inner fish pond, far left and inside right. But when taking richness survey data we used the highest number of observations and when taking the size data we used a small rock 3cm in size and placed it on the nursery so as to estimate size; and we classified them opportunistically so standard deviation isn’t necessary.
Data
https://docs.google.com/document/d/1LmZSOaD4YEh7sJmy8pC6VnOkvRDZvcdIu7gYCr1re3s/edit?usp=sharing
Discussion
Species richness was highest in the fish pond, particularly, inside of the central structure which was home to a variety of juvenile butterflyfish, gregories, and surgeonfish. Outside the fish pond, the majority juvenile observed were those of previously mentioned dusky gregories that made their home in tiny rock shelters.
Richness was much lower outside comparatively. There was a mix of both juvenile and adult fish of many families present, interestingly including a juvenile snowflake moray eel adult yellow boxfishm a meter and a half long flutemouth that was swimming among the fish pond’s interio, and an adult orange-lined triggerfish lodged within a solitary rock. In total, the fish pond was home to 15 different families of reef fish. In comparison directly outside of the fish pond there were 7 families on the right exterior and 5 on the left exterior.
The left area of the pond was notably more abundant in life than the right side. We propose this could possibly be due to the current going from south (left) to north (right) causing more sediment deposits on the left side. But further research is required to determine this hypothesis. On the left we observed 7 raccoon butterflyfish, three juvenile scissortail sergeants, and a solitary peacock damselfish. The right exterior meanwhile was relatively barren. Notably, however, it was one of the only locations where lagoon triggerfish were observed. Three juveniles that used the rock holes on the bottom for shelter.
In terms of abundance the Dusky gregories were by far the most abundant species in the area, living in practically every facet of the rock walls. Most were large, 6-7 cm adults that guarded their territories fiercely. Dusky gregories were observed constantly fighting back against other fish, including one scaring off an entire shoal of grazing sharpnose mullets. Furthermore, the presence of predatory fish like the flutemouth or eels could indicate attempts at predation which may be of interest to understanding the fish pond’s ecosystem. Butterflyfish like the vagabond and raccoon were spotted most often with a few speckled butterflyfish and a single threadfin butterflyfish being observed.
We would like to note that during our first day of surveying, there was a high in current due to the wind and weather conditions making the water have low visibility. The current also pushed surveyors so it was hard to maintain the set meter distance from our transects. The second day was better in visibility but current still posed a problem and we would recommend further research done on better weather conditions.
The fish pond’s diversity is certainly above that of the adjacent areas, being home to even large adult fish species. The presence of juvenile butterflyfish and damselfish indicates that it’s functioning as intended as a nursery for these species, indicating that it’s recruiting and maintaining young fish sufficiently well. For future surveys, we suggest broadening the scope of surveyed families to include all types of fish. Juvenile surgeonfish, eels, flutemouths, and emperor angelfish were also found in and around the fish pond. Looking further into their quantities compared to outside the pond will better quantify what thrives and relies on this miniature ecosystem. Furthermore, the behavior of specimens within the fish pond could be of potential interest. How often are they feeding? What is their alert and flight distance? How territorial are they? Compare all this to like specimens outside. Perhaps those in the fish pond feed more and are more territorial due to the limited space. It’s clear the fishpond is providing a unique and valued service for the coral reef community, and focusing on the behaviors and physiology of its inhabitants may yield valuable information regarding the function of fish ponds.
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