Jellyfish Lake Conditions and Forecast
CRRF provides a forecast of what to expect in the next 3 months in Jellyfish Lake, based on current conditions of the lake, jellyfish population and weather forecasts.
MONITORING DATE: Dec 16, 2025
JELLYFISH NUMBERS
+100,000
500-100,000
1-500
0
COMPARED TO PAST 3 MONTHS
COMPARED TO PAST 3 MONTHS
Jellyfish Lake Current Conditions and Forecast
CRRF provides a forecast of what to expect in the next 3 months in Jellyfish Lake, based on current conditions of the lake, jellyfish population and weather forecasts.
MONITORING DATE: Dec 16, 2025
JELLYFISH NUMBERS
+100,000
500-100,000
1-500
0
COMPARED TO PAST 3 MONTHS
CURRENT WATER TEMPERATURE (AVERAGE 0-12M)
32.0 oC / 89.6 oF
COMPARED TO PAST 3 MONTHS
CURRENT ENSO PHASE
La Niña
KEY
LEVELS
Green – Jellyfish present; conditions favor presence of jellyfish for the next 3 months.
Yellow – Jellyfish present; conditions predict numbers decreasing for the next 3 months.
Orange – Jellyfish absent; conditions favor jellyfish return in the next 3 months.
Red – Jellyfish absent; conditions do not favor jellyfish return in the next 3 months.
COMPARED TO PAST 3 MONTHS
Downward arrow – Jellyfish or temperature decreasing
Upward arrow – Jellyfish or temperature increasing
Dash – Same, no change
This page reports current conditions in Jellyfish Lake based on monthly or quarterly monitoring. Golden jellyfish numbers below 80,000 are based on visual surveys, and greater than >80,000 are based on net hauls (Click here to learn more about how we count jellyfish). It also provides a forecast of what to expect in the next 3 months based on current conditions of the lake, the jellyfish population, and climate and weather forecasts. Forecasts are meant as a guide, but not as “an absolute truth.”
If the lake is cooling, the forecast tends to be favorable for Golden jellies. If the lake is heating up, the forecast tends to be unfavorable.
INCIDENT REPORT
Tour guides and visitor observations are a valuable contribution, because you visit the lake more often than our monthly visits. Please report here, if you see bleached jellyfish or notice fewer numbers of jellyfish, see a crocodile or trash, or if you see something “new” or “different” that could be an introduced species.
FREQUENTLY ASKED QUESTIONS
How do you count jellyfish?
We use nets to catch jellyfish at 15 different stations equally spaced in the lake, from one end to the other. At each station, we drop the net to 15m, and slowly pull it up towards the surface to catch jellyfish. At the end of each run (all 15 stations), we count the number of jellyfish we caught and measure their bell diameter. We complete three runs in one day. We use the mean of our catch for the day, multiplied by the area of the lake, to estimate how many Golden jellyfish are in the lake.
How does water temperature affect the Golden jellyfish?
Lake water temperature is the primary factor influencing Golden jellyfish abundance. When the lake starts warming up, fewer Golden jellyfish are present and bleached jellyfish are observed. Once the lake becomes too warm, no new jellyfish are produced, and the old ones eventually die. When the lake is cool, we see more smaller Golden jellyfish (0.5cm–2cm) in the lake.
How does the weather and climate affect the lake and Golden jellyfish?
Changes in weather and climate can affect the lake and the Golden jellyfish. Drought can increase salinity (how much salt is in water) in Jellyfish Lake. Heavy rainfall can a result in a freshwater lens from the surface to 5m, and with little to no wind, this can lead to an increase in water temperature at 6m. Wind energy can help cool the lake down. These changes in lake conditions can lead to changes in jellyfish abundance.
What factors do we use to make our forecasts?
We use data on:
- Temperature, salinity and oxygen of Jellyfish Lake and jellyfish abundance (collected during monitoring visits).
- Rainfall and wind speed collected by our weather station on Ngeanges Island.
- Lagoon water temperature and water pressure (proxy for sea level) collected by loggers in Malakal Harbor.
- Season – time or month of the year.
- 3 Month Forecast from Palau’s National Weather Service for predictions on rainfall, water temperature, and El Niño Southern Oscillation (ENSO) events (El Niño/La Niña).
How can you help?
We can all do our part in protecting Jellyfish Lake, by doing the following:
- SUPPORT our monitoring research: your donations will help protect Jellyfish Lake!
- Empty your pockets. Do not carry anything from the ocean into the lake, including rocks and shells.
- Use reef-safe sunscreen and apply it 30 minutes before entering the lake.
- Swim gently in the lake to make sure you do not damage the jellyfish.
Web interface supported by: USGS Pacific Climate Adaptation Science Center
This function has been disabled for Coral Reef Research Foundation.