The Impact of Parasail Boats on
the Hawaiian Humpback Whale
(Megaptera novaeangliae)

Marsha L. Green

Paper prepared for Marine Mammal Commission Hearings, March, 1990 Honolulu, Hawaii. Paper presented at annual meeting of the Animal Behavior Society, June, 1991, Wilmington, NC.

Increasing levels of tourism in the past decade and the resulting increase in vessel traffic in the habitat of humpback whales in Hawaii have caused heightened scientific and public concern about the impact of boats on this endangered species. There is little evidence to suggest either a marked increase or decrease in the number of humpback whales since their protection by international agreement in 1966. Baker et al, 1987 suggest the lack of recovery may be due to a depressed reproductive rate of female humpback whales. The causes of this depressed reproductive success are not known at present but may be related to the increase in vessel traffic.

The near-shore areas appear to be preferred habitat of cow/calf pods throughout the Hawaiian islands (Herman and Antinoja, 1977, Glockner-Ferrari and Ferrari, 1985). Evidence indicates that cow/calf pairs prefer the shallow, protected waters for resting, nursing, and possibly avoiding sharks and disturbance form other whales (Glockner-Ferrari and Ferrari, 1985). However, Ferrari's 1985 data indicates that cow/calf pods have been moving offshore since 1977. Abandonment of near shore waters could be harmful to the recovery of the Hawaiian humpback whale population as the area available for calving may be a critical factor in determining the eventual size of the population.

This is a report of one part of a comprehensive research program on the impact of vessels on the Hawaiian humpback whale. The report includes data collected from two shore-based observation platforms in west Maui on twelve mornings between January 15th and January 28th, 1990.

The researched design allowed us to compare the number, distribution, and behavior of pods of whales in two near-shore areas, one with and one without parasail boat operations. Olowalu Hill, a traditional research location, served as a control area free of parasail operations. Data collected at Olowalu was used as an indication of the expected probability of sighting and following whales within a specified area and time period along the west Maui coast when no parasail boats are present. These observations were compared to similar ones gathered from the roof of the Hyatt hotel which includes the Kaanapali parasail area. At the Hyatt we also compared the number, distribution and behavior of whales before and after parasail operation each morning. In addition there were five rainy mornings when parasails did not operate at all which allowed us to compare entire mornings with and without parasail boats at the Hyatt. This experimental design allowed us to isolate the effect of parasail operations on whale presence or absence and whether or not whales disappeared when parasail boats began operating.

Method

There was a minimum of five people on each research team. One person specialized in operating a theodolite used to track whales and boats, one person recorded the data, and three people spotted whales and boats with binoculars. At the Hyatt one person recorded parasail activity. Each morning teams conducted three 15-minute scan samples during which the locating of all whales and boats were recorded at Olowalu and at the Hyatt. Teams also recorded the behavior of a focal pod near the shore station for as long as they remained visible. Observations normally began at 8:30 A.M. and continued until 12 noon.

For data analysis we used the jet ski platform anchored about 620 meters offshore at the Hyatt as a water-based reference point form which we calculated distances of pods of whales. The target area was defined as the water within a 2000 meter radius of the jet ski platform. We selected a reference point the same distance from shore at a comparable shoreline contour off Olowalu and used it to define a control target area of the same size. The shoreline configurations of the two sites are very similar. This slide shows both shorelines, the location of the water-based reference point, and the target area at Olowalu and the Hyatt. Pods sighted within the target areas were used in the data analysis. If a pod was present within the target area it was chosen as the focal pod. Otherwise, the pod closest to the shore station was chosen.

Results

On seven out of the twelve observation mornings, we saw one or more pods of whales within 2000 meters of the jet ski platforms at the Hyatt before jet skis began operating. The seven times we saw pods within the target area at the Hyatt were either during the first sample before parasail boats began operating. The seven times we saw pods within the target area at the Hyatt were either during the first scan sample before parasail boats began operation (three times) or on four rainy mornings when the parasail boats did not operate at all (four times). We never saw a pod within the target area when parasails were operating.

Table 1 summarizes the number of mornings pods were seen within 2000 meters of the actual location of the jet ski platform at the Hyatt and the comparable target area of Olowalu before and after parasail boats operated. A morning was counter as a "whales present before operation" if a pod was spotted within the 2000 meter radius during the first scan before parasail operation of if a pod was spotted at any time during the morning on the five days the parasails did not operate at all. A morning was counter as "whales present after operation" if a pod was spotted at any time during the seven mornings after the parasails began to operate at the Hyatt.

Table 1

Number of Mornings Pods Were Sighted Within the Target Areas Before and After Parasail Boats

The operation of parasail boats significantly decreased the probability of sighting a pod within the target area at the Hyatt on any given morning, X^2(1,N-19)-17.17.31, p<.001. However, the probability of sighting a pod within the target area at Olowalu on the same days before and after parasail operation was not significantly different, X^2(1,N-19)-2.16. Yates correction for continuity was used on the chi square tests because of low expected frequencies.

Table 1 also indicates that the probability of seeing a pod within the target area before parasail boats was operated was comparable at the two locations. At the Hyatt the probability was .58 and at Olowalu it was .67. However, after parasail boats began operation the probability of seeing a pod within the target area became 0. The probability of seeing a pod within the target area at Olowalu at matching times was .86.

Table 2 compares the total number of pods sighted within the target areas at Olowalu and the Hyatt before and after the operation of parasail boats.

Table 2

Total Number of Pods Sighted Within the Target Areas Before and After Parasail Boats.

Again, the total number of pods sighted was comparable at the two locations (ten at each site) before parasail boats operated but significantly different after operation began. Parasail operation significantly reduced the total number of pods sighted within the target area at the Hyatt as compared to the other three conditions, X^2(1,N-27)-17.47, p<.001. (Yates correction for continuity was used)

We sighted pods on twelve mornings but followed focal pods on only eleven of the twelve days. We were able to follow a focal pods within the target area at the Hyatt on four of these eleven mornings. These 4 mornings were days the parasails did not operate due to inclement weather. On each of these four mornings the pods were cow/calf pods milling at the surface. At Olowalu, we were able to follow a focal pod within the target area on 9 of the 11 mornings.

Table 3 indicates that the probability of being able to follow a focal pod within the target area was .80 at both Olowalu and the Hyatt on mornings when parasail boats did not operate (four of five mornings at the Hyatt and four of the same five mornings at Olowalu). When parasail boats did operate the probability of following a focal pods within the target area became 0 at the Hyatt (0 out of 6 mornings) but remained high at Olowalu at .83 (five out of the six mornings). There was a significantly reduced probability of following a focal pod within the target area at the Hyatt on days the parasail boats operated, X^2(1,N-13)-4.33, p<.05. (Yates correction for continuity was used.)

Table 3

Probability of Following a Focal Pd Within the Target Area at the Hyatt
With and Without Parasail Boats and on Matched Days at Olowalu.

To see if an increase in boat traffic other than parasail boats might be related to the significant decrease in the number of pods sighted in the target area at the Hyatt after parasails began to operate, we counter the total number of boats within 2000 meters of the pods when they were initially sighted. These mornings when pods were sighted are called "whale days" and parasail boats were never operating when the whales were initially sighted.

Each "whale day" was matched with a "no whale day" at the Hyatt which was, when possible, the same day of the week (to control for increased weekend traffic) but a day when no pods were present within the target area at the time of sighting the pod on the "whale day". We then compared the number of boats sighted within 2000 meters of the pods on "whale days" with the number of boats, other than parasails, present within the same area and at the same time on "no whale days". A total of ten boats were present within the same area and at the same time on "no whale days". A total of ten boats were present within 2000 meters of the pods on "whale days" and nine boats were present within the comparable areas on "no whale days". Consequently, the significant reduction in pods spotted during parasail operation at the Hyatt cannot be attributed to any correlated change or increase in general level of vessel traffic.

It is also unlikely that other factors such as time of day or changing weather conditions were related to the significant changes in whale distribution and behavior at the Hyatt since similar changes did not occur at the same time in the control area at Olowalu. While the frequencies for the chi square tests are low, the fact that the observed frequencies showed significant differences on all four tests ever after the conservative Yates correlation suggests a stronger effect of parasail boats on whale distribution than one that was based on large numbers of observations (Spence, Cotton, Underwood & Duncan, 1990, p. 185).

Discussion

The surprisingly high and comparable probabilities of sighting whales and follow focal pods within the target areas at Olowalu and the Hyatt when parasails were not operating indicates that the area around the Hyatt is an important near-shore habitat for whales. In addition, the regularity with which cow/calf pods were seen milling within 2000 meters of the jet ski platform at the Hyatt on mornings when parasail boats did not operate at all (four out of five mornings or 80% of the time) suggests that the area is a preferred cow/calf resting spot. It seems unlikely that the probability of sighting a milling cow/calf pod within a 4000 meter diameter circle would be as high as 80% at most mother points along the west Maui coast on any given morning. Previous observations at Olowalu suggest it is an area frequented by cow/calf pods and the probability of sighting a cow/calf pod within the target area at Olowalu on the same five morning was 60%.

The complete absence of whale sighting and of focal pods within the target area at the Hyatt only when parasails were operating indicates that parasail boats displace whales including cow/calf pods form this desirable near shore area. While it is impossible to know for certain whether or not this displacement will affect the long term recovery of the endangered humpback whale, the prudent course of action would be to stop harassing the whales.

We sent this data to the Hawaii State Legislature in March of 1990. Last summer they passed a bill banning the operation of parasail boats and jet skis in west Maui and 2 other Hawaiian coastal areas from December 15 to May 15 each year during whale season. Consequently, parasail boats did not operate in west Maui this winter.

References

Glockner-Ferrari, D. and Ferrari, M. (1985). Individual identification, behavior, reproduction, and distribution of humpback whales (Megaptera novaeangliae) in Hawaii. Marine Mammal Commission Report, Contract MM2629753-5.

Herman, L.M. and Antinoja, R. C. (1977). Humpback whales in the Hawaiian breeding waters: Population and pod characteristics. Whales Research Institute, Tokyo, Japan. Scientific Reports, 29, 59-85.

Spence, J. T., Cotton, J. W., Underwood, B. J. & Duncan, C. P. (1990) Elementary Statistics (5th ed.). Englewood Cliffs, N.J.: Prentice Hall.

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