How Do Researchers Estimate the Number of Humpback Whales Visiting Samaná Bay Each Season?

Every winter, humpback whales arrive in the waters around Samaná Bay in the Dominican Republic. Their presence attracts visitors, tour operators, conservationists, and marine researchers who want to understand how these magnificent animals use the region.

One important scientific question is how many humpback whales visit Samaná Bay during a season.

Counting whales may sound simple, but it is much more complicated than counting animals in a field. Whales spend much of their time underwater, move across large areas, and may appear at different locations on different days. The same whale can also be photographed by several boats, creating a risk of counting it more than once.

Researchers therefore use several methods to estimate whale numbers and understand how the population uses these waters.

Why Is Counting Humpback Whales Difficult?

Humpback whales are large, but their size does not make them easy to count accurately.

A whale may surface briefly before diving again. Another may remain underwater while nearby animals are visible. Weather, waves, visibility, and the distance between observation points can affect how many whales researchers detect.

There is also a difference between counting sightings and counting individual animals.

For example, a whale observed on Monday and photographed again on Thursday might represent two sightings of one animal rather than two different whales. Without reliable identification or an appropriate statistical method, adding every sighting together could produce an inflated estimate.

Scientists must account for these challenges before drawing conclusions about the number of whales visiting the bay.

1. Conducting Systematic Whale Surveys

One way to estimate whale numbers is through systematic surveys.

Researchers follow a planned observation method, recording whale sightings along selected routes or within defined areas. Depending on the study, observations may be conducted from boats, aircraft, or other suitable platforms.

During a survey, researchers may record:

• The location of each sighting.
• The number of whales observed together.
• The time and date of the observation.
• Weather and sea conditions.
• Whether calves are present.
• The direction in which the whales are moving, when it can be determined.

Using a consistent method helps researchers compare observations across different days, locations, or seasons.

However, a survey does not necessarily detect every whale in the study area. Scientists must consider the possibility that some animals were underwater, outside the observation route, or otherwise missed.

2. Photographing Whale Tail Flukes

Photo identification is a valuable technique for studying humpback whales.

The underside of a humpback whale's tail flukes often displays distinctive patterns of pigmentation, scars, and other markings. Researchers can photograph these features and compare them with images collected previously.

When photographs provide enough detail, scientists may be able to match an animal to an existing identification record.

This helps researchers answer several questions:

• Has this whale been seen in Samaná Bay before?
• Was the same whale photographed at another location?
• How often is an identified whale observed during a season?
• Does the whale appear in records from different years?

Photo identification is especially useful for separating individual whales from repeated sightings.

Nevertheless, not every photograph produces a confident match. Poor lighting, an unclear angle, damaged images, or changes in visible markings can make identification difficult.

3. Using Mark-Recapture Methods

Researchers sometimes use a statistical approach called capture-recapture, also known as mark-recapture. In whale studies, photographic identification can serve as a non-invasive way to recognize previously observed animals.

The basic idea is to compare individuals identified during separate sampling periods.

Imagine that researchers photograph a group of whales during one survey. On a later survey, they photograph another group and check how many individuals were already recorded.

If many whales in the second sample have appeared in the first sample, that overlap can help researchers estimate the wider population under suitable statistical assumptions.

A simplified estimator sometimes used to explain the method is:

Estimated population = (first sample × second sample) ÷ number of previously identified individuals found again

For example, suppose the first sample contains 40 identified whales, the second contains 50, and 10 whales appear in both samples.

The simplified estimate would be:

40 × 50 ÷ 10 = 200 whales.

This is an illustrative mathematical example, not an actual estimate for Samaná Bay.

Real studies may use adjusted estimators and more sophisticated models. The method depends on assumptions about sampling, identification accuracy, and the population being studied. Migration into or out of the study area can complicate the calculation.

4. Recording Groups Without Double-Counting

Humpback whales may travel alone or appear in temporary groups. During whale-watching season, a boat could encounter several animals in one area and another group farther along its route.

Researchers must distinguish between the number of whales present at one moment and the number of different whales observed throughout a longer period.

They may use photographs, timestamps, geographic coordinates, and detailed sighting records to compare encounters.

For instance, if a whale photographed in the morning is recognized later that afternoon, researchers can avoid automatically treating the second encounter as a new individual.

Group membership can change, however, and some whales may not be identifiable from available images. Scientists therefore document uncertainty rather than assuming every sighting can be matched perfectly.

5. Estimating Whales That Researchers Do Not See

Even carefully planned surveys can miss animals.

A whale might be underwater when observers pass nearby, or it may be too far away to detect reliably. Researchers refer to this general issue as imperfect detection.

Some studies use statistical models to account for the likelihood that animals were present but not observed.

The appropriate method depends on the research design. For example, scientists may use distance-sampling approaches when they can measure distances to detected animals and make suitable assumptions about detection. Other studies may use repeated observations, photographic records, or models designed for populations that move between locations.

These methods are important because the number of whales observed directly is not always equal to the number of whales present.

A scientifically useful estimate should explain how observations were collected, what the method accounts for, and how uncertain the final result may be.

6. Comparing Whale Numbers Across Different Seasons

Researchers may compare estimates from multiple years to investigate how whale use of Samaná Bay changes over time.

Such comparisons can help address questions about seasonal attendance, population trends, and changes in the timing or distribution of sightings.

However, the comparison must be fair.

A season with more survey days, better weather, or more extensive observation coverage might produce more sightings than a season with limited research effort, even if the number of whales visiting the area has not changed.

Researchers therefore consider factors such as:

• The number of survey days.
• The geographic area covered.
• Differences in observation conditions.
• Changes in survey methods.
• The likelihood of detecting whales.
• The possibility of seeing the same animals repeatedly.

A rise or fall in raw sightings alone does not necessarily demonstrate that the whale population has increased or decreased.

Consistent methods and suitable statistical analysis make year-to-year comparisons more meaningful.

7. Why Whale Counts Matter for Conservation

Reliable whale estimates help scientists and conservation organizations understand how marine habitats are being used.

Population studies can contribute to the evaluation of long-term trends, the identification of important habitats, and decisions about where additional research or protective measures may be needed.

In a whale-watching destination such as Samaná Bay, scientific information can also help explain why responsible tourism matters.

Boats should follow applicable regulations and responsible viewing practices, avoid disrupting whale behavior, and respect the instructions of trained captains and guides.

Tour operators and visitors can also contribute to public awareness by appreciating that a whale sighting is part of a larger ecological picture.

Responsible behavior cannot replace formal scientific monitoring, but it can help reduce avoidable disturbance while people enjoy observing these animals.

8. Can Whale-Watching Tour Operators Count the Entire Population?

No. A tour operator may record valuable sightings, but observations from ordinary whale-watching trips do not automatically represent a complete population survey.

Tour boats may travel along routes selected to find whales rather than routes designed to sample an entire area consistently. Several boats may also encounter the same whale on the same day.

Research-grade estimates require a suitable study design, documented observation effort, appropriate identification or statistical methods, and an assessment of uncertainty.

Sightings reported by tour operators can still be useful, especially when records are collected systematically and shared with qualified researchers. Their scientific value depends on how the information is recorded, verified, and analyzed.

Frequently Asked Questions

How do scientists count humpback whales in Samaná Bay?

They may combine systematic surveys, photographic identification, repeated observations, and statistical models. The method depends on the research question and the available data.

Why can't researchers simply count every whale they see?

Some whales remain underwater or go undetected, and individual animals may be observed more than once. Researchers must account for both missed animals and repeated sightings.

Are photographs useful for estimating whale populations?

Yes. Photographs of distinctive tail-fluke patterns can help researchers recognize individual humpback whales and compare sightings across locations and seasons.

Does a higher number of sightings mean there are more whales?

Not necessarily. More sightings may result from increased survey effort, better visibility, or whales spending more time near observation routes. Scientists need appropriate comparisons before concluding that population size has changed.

Can scientists estimate the exact number of whales visiting Samaná Bay?

An exact count is not always possible. Researchers usually report estimates with uncertainty, and the result depends on the study area, time period, survey methods, and quality of the data.

Why are long-term whale records important?

Records collected over multiple seasons help scientists distinguish short-term variation from longer-term changes in whale distribution and population trends.

Conclusion

Estimating the number of humpback whales visiting Samaná Bay requires more than counting animals that appear at the surface. Researchers must account for underwater behavior, repeated sightings, missed detections, and the movement of whales through the region.

Systematic surveys, photo identification, mark-recapture methods, and statistical models provide different ways to investigate whale numbers. Each method has strengths and limitations, so careful study design and transparent reporting are essential.

For visitors to Samaná, understanding these methods adds another dimension to whale watching. Every sighting is a memorable experience, but when observations are documented and analyzed carefully, they can also contribute to a broader understanding of these remarkable marine mammals.