The use of auditory stimulants during swim encounters with Hector's dolphins (Cephalorhynchus hectori hectori) in Akaroa Harbour,New Zealand

The coastal distribution of Hector's dolphins and their attraction to vessels make them easily accessible to commercial tour operations. For over 25 yr, tour operators have been undertaking view and swim‐with‐dolphin trips in Akaroa Harbour, New Zealand. Since 2003, auditory stimulants, in particular stones, have been provided during such swim encounters. The potential effects associated with such stimulants have not, until now, been examined. Here, we investigate the effects of stones and other human‐induced noise on Hector's dolphin behavior. The use of stones significantly affected how dolphins interacted with swimmers. Specifically, swimmers who used stones had a greater probability of close approaches by dolphins than those who sang or simply floated on the surface of the water. The number of close and sustained approaches was also significantly higher for swimmers using stones. Dolphins were more interactive with active swimmers, approaching closer and engaging for longer than with nonactive swimmers. Dolphins socializing had a tendency to be engaged longer with swimmers. The use of stones as an auditory stimulant to sustain or enhance interactions with dolphins by artificial means may not be in the best interest of an endangered species, which already faces a range of challenges due to human activity.     

Behavioural Responses of Dusky Dolphin Groups (Lagenorhynchus obscurus) to Tour Vessels off Kaikoura, New Zealand

Background

Commercial viewing and swimming with dusky dolphins (Lagenorhynchus obscurus) near Kaikoura, New Zealand began in the late 1980s and researchers have previously described changes in vocalisation, aerial behaviour, and group spacing in the presence of vessels. This study was conducted to assess the current effects that tourism has on the activity budget of dusky dolphins to provide wildlife managers with information for current decision-making and facilitate development of quantitative criteria for management of this industry in the future.

Methodology/Principal Findings

First-order time discrete Markov chain models were used to assess changes in the behavioural state of dusky dolphin pods targeted by tour vessels. Log-linear analysis was conducted on behavioural state transitions to determine whether the likelihood of dolphins moving from one behavioural state to another changed based on natural and anthropogenic factors. The best-fitting model determined by Akaike Information Criteria values included season, time of day, and vessel presence within 300 m. Interactions with vessels reduced the proportion of time dolphins spent resting in spring and summer and increased time spent milling in all seasons except autumn. Dolphins spent more time socialising in spring and summer, when conception occurs and calves are born, and the proportion of time spent resting was highest in summer. Resting decreased and traveling increased in the afternoon.

Conclusions/Significance

Responses to tour vessel traffic are similar to those described for dusky dolphins elsewhere. Disturbance linked to vessels may interrupt social interactions, carry energetic costs, or otherwise affect individual fitness. Research is needed to determine if increased milling is a result of acoustic masking of communication due to vessel noise, and to establish levels at which changes to behavioural budgets of dusky dolphins are likely to cause long-term harm. Threshold values from these studies would allow managers to set appropriate operational conditions based on quantifiable criteria.     

Predictive Modeling of Spinner Dolphin (Stenella longirostris) Resting Habitat in the Main Hawaiian Islands

Predictive habitat models can provide critical information that is necessary in many conservation applications. Using Maximum Entropy modeling, we characterized habitat relationships and generated spatial predictions of spinner dolphin (Stenella longirostris) resting habitat in the main Hawaiian Islands. Spinner dolphins in Hawai'i exhibit predictable daily movements, using inshore bays as resting habitat during daylight hours and foraging in offshore waters at night. There are growing concerns regarding the effects of human activities on spinner dolphins resting in coastal areas. However, the environmental factors that define suitable resting habitat remain unclear and must be assessed and quantified in order to properly address interactions between humans and spinner dolphins. We used a series of dolphin sightings from recent surveys in the main Hawaiian Islands and a suite of environmental variables hypothesized as being important to resting habitat to model spinner dolphin resting habitat. The model performed well in predicting resting habitat and indicated that proximity to deep water foraging areas, depth, the proportion of bays with shallow depths, and rugosity were important predictors of spinner dolphin habitat. Predicted locations of suitable spinner dolphin resting habitat provided in this study indicate areas where future survey efforts should be focused and highlight potential areas of conflict with human activities. This study provides an example of a presence-only habitat model used to inform the management of a species for which patterns of habitat availability are poorly understood.     

Fine‐scale habitat use in Indo‐Pacific humpback dolphins,Sousa chinensis,may be more influenced by fish rather than vessels in the Pearl River Estuary,China

Shifts in habitat use and distribution patterns in dolphins are often concerns that can result from habitat degradation. We investigated how potential changes to a habitat from human activity may alter dolphin distributions within Lingding Bay in the Pearl River Estuary, China, by studying the relationship between fish choruses, vessel presence and Indo‐Pacific humpback dolphin (Sousa chinensis) detection rates. Analyses revealed temporal and spatial variation within fish choruses, vessel presence and dolphin detection rates. After accounting for any temporal autocorrelation, correlations between fish choruses and dolphin detection rates were also found; however, no relationship between fish choruses and vessel presence or dolphin detection rates and vessel presence were observed. Furthermore, fewer dolphins were detected at sites where fish activity was less intense. Thus fish activity, rather than vessels, may be a key factor influencing the distribution of the dolphins within the estuary. These findings emphasize the risk of potential shifts in habitat use for Indo‐Pacific humpback dolphins due to detrimental changes to prey availability and dolphin feeding grounds from human activity, such as overfishing and coastal developments, within the estuary. This is a critical conservation issue for this dolphin population that is facing intense anthropogenic pressure.     

Why Do Dolphins Form Mixed‐Species Associations in the Azores?

Mixed‐species associations are temporary associations between individuals of different species that are often observed in birds, primates and cetaceans. They have been interpreted as a strategy to reduce predation risk, enhance foraging success and/or provide a social advantage. In the archipelago of the Azores, four species of dolphins are commonly involved in mixed‐species associations: the common dolphin, Delphinus delphis, the bottlenose dolphin, Tursiops truncatus, the striped dolphin, Stenella coeruleoalba, and the spotted dolphin, Stenella frontalis. In order to understand the reasons why dolphins associate, we analysed field data collected since 1999 by research scientists and trained observers placed onboard fishing vessels. In total, 113 mixed‐species groups were observed out of 5720 sightings. The temporal distribution, habitat (water depth, distance to the coast), behaviour (i.e. feeding, travelling, socializing), size and composition of mixed‐species groups were compared with those of single‐species groups. Results did not support the predation avoidance hypothesis and gave little support to the social advantage hypothesis. The foraging advantage hypothesis was the most convincing. However, the benefits of mixed‐species associations appeared to depend on the species. Associations were likely to be opportunistic in the larger bottlenose dolphin, while there seemed to be some evolutionary constraints favouring associations in the rarer striped dolphin. Comparison with previous studies suggests that the formation of mixed‐species groups depends on several environmental factors, and therefore may constitute an adaptive response.     

Where to catch a fish? The influence of foraging tactics on the ecology of bottlenose dolphins (Tursiops truncatus) in Florida Bay,Florida

Observations of bottlenose dolphins ( Tursiops truncatus ) in Florida Bay, Florida, between 2002 and 2005 revealed the use of three distinct foraging tactics. The goal of this study was to identify ecological correlates with tactic use and describe the impact of foraging specializations on the overall habitat use and distribution patterns of this dolphin population. Foraging tactics showed strong association with contrasting environmental characteristics, primarily depth. Locations of two of these tactic groups were spatially repulsed. Analyses of sighting histories of individual dolphins observed at foraging events determined that dolphins which employed one tactic never employed the other, and vice versa . Although bottlenose dolphins have plastic foraging behaviors, dolphins in Florida Bay appear to specialize in one tactic and subsequently limit their overall distribution patterns to coincide with habitats that facilitate success using that foraging tactic. This study demonstrates how foraging behavior can be an ecological determinant of overall dolphin habitat use patterns and works to create spatial structure within a population due to consistent mapping of tactics onto environmental variation. These foraging specializations potentially impact the social and demographic patterns of this dolphin population. The possible evolutionary mechanisms behind this intraspecific variation, including resource limitation and social learning, are considered.     

Population genetic structure and taxonomy of the common dolphin (Delphinus sp.) at its southernmost range limit: New Zealand waters

New Zealand is the southernmost limit of the common dolphin's (genus Delphinus) distribution in the Pacific Ocean. In this area, common dolphins occur in both coastal and oceanic habitats, exhibit seasonal and resident occurrence, and present high morphological variability. Here we investigated the population structure and the taxonomic identity of common dolphins (Delphinus sp.) within New Zealand waters using 14 microsatellite loci, 577 bp of the mtDNA control region, and 1,120 bp of the mtDNA cytochrome b gene across 90 individuals. We found high genetic variability and evidence of population expansion. Phylogenetic analyses conducted to clarify the taxonomic status of New Zealand common dolphins did not show any clustering reflecting geographic origin or morphotypes. The microsatellite analysis showed genetic differentiation between Coastal and Oceanic putative populations, while mtDNA revealed significant genetic differentiation only between the Hauraki Gulf and other putative groups. Our results suggest that differences in habitat choice and possible female site fidelity may play a role in shaping population structure of New Zealand common dolphins.     

DUSKY DOLPHIN (LAGENORHYNCHUS OBSCURUS) FORAGING IN TWO DIFFERENT HABITATS: ACTIVE ACOUSTIC DETECTION OF DOLPHINS AND THEIR PREY

Active-acoustic surveys were used to determine the distribution of dusky dolphins and potential prey in two different New Zealand locations. During seven survey days off Kaikoura Canyon, dusky dolphins were found within the DeepScattering Layer (DSL) at 2000 when it rose to within 125 m of the surface. As the DSL rose to 30 m at 0100, the observed depth of dolphins decreased, presumably as the dolphins followed the vertical migration of their prey. Acoustically identified subgroups of coordinated animals ranged from one to five dolphins. Time, depth of layer, and layer variance contributed significantly to predicting foraging dusky dolphin subgroup size. In the much shallower and more enclosed Admiralty Bay, dolphins noted at the surface as foraging were always detected with the sonar, but were never observed in coordinated subgroups during the brief (two-day) study there. In Admiralty Bay dolphin abundance was correlated with mean volume scattering from potential prey in the water column; and when volume scattering, an index of prey density, was low, dolphins were rarely present. Ecological differences between the deep waters of Kaikoura Canyon and the shallow nearshore waters of Admiralty Bay may result in differences in how, when, and in what social groupings dusky dolphins forage.     

Selection of critical habitats for bottlenose dolphins (Tursiops truncatus) based on behavioral data,in relation to marine traffic in the Istanbul Strait,Turkey

Marine traffic is a significant source of disturbance to the bottlenose dolphin population in the Istanbul Strait, Turkey. To determine the importance of this threat, behavioral data together with sighting data of both dolphins and marine vessels were assessed for 2012. The current study suggests that the Istanbul Strait is used mostly as a foraging ground for bottlenose dolphins. Nonetheless, in the same area there is intense marine traffic as well as increase of industrial fishing activities in autumn. The findings of this study indicated that high‐speed ferries and high‐speed boats were the most significant source of disturbance. Moreover, increased densities of fishing vessels resulted in a drastic decline of dolphin sightings. This study highlights that vessel type, speed, distance, and density have a cumulative negative effect on dolphins. In order to mitigate the impacts of vessels, it is necessary to establish managed areas in the Istanbul Strait. Such proposed areas should limit speed and density of marine traffic and have specific restrictions on vessel routes. We propose three different seasonal managed areas according to their values as critical habitat for bottlenose dolphins in the strait.     

Restricted dispersal in a continuously distributed marine species: common bottlenose dolphins Tursiops truncatus in coastal waters of the western North Atlantic

The marine environment provides an opportunity to examine population structure in species with high dispersal capabilities and often no obvious barriers to genetic exchange. In coastal waters of the western North Atlantic, common bottlenose dolphins, Tursiops truncatus, are a highly mobile species with a continuous distribution from New York to Florida. We examine if the highly mobile nature coupled with no obvious geographic barriers to movement in this region result in a large panmictic population. Mitochondrial control region sequences and 18 microsatellite loci indicate dolphins are partitioning the habitat both latitudinally and longitudinally. A minimum of five genetically differentiated populations were identified among 404 samples collected in the range of New Jersey to northern Florida using both genetic marker types, some inhabiting nearshore coastal waters and others utilizing inshore estuarine waters. The genetic results reject the hypothesis of a single stock of coastal bottlenose dolphins put forth after the 1987–1988 epizootic that caused a large‐scale die‐off of dolphins and suggest instead the disease vector was transferred from one population to the next as a result of seasonal migratory movements of some populations. These coastal Atlantic populations also differ significantly from bottlenose dolphin samples collected in coastal waters of the northern Gulf of Mexico, implying a long‐term barrier to movement between the two basins.     

Behavior of free-ranging common dolphins (Delphinus sp.) in the Hauraki Gulf, New Zealand

Here we present the first data describing the behavior of common dolphins ( Delphinus sp.) in the Hauraki Gulf, New Zealand. Activity budgets are used to assess the effects of diel, season, depth, sea surface temperature, group size, and composition on dolphin behavior. Additionally, the presence/absence of Bryde's whale ( Balaenoptera brydei ) and Australasian gannet ( Morus serrator ) is examined in relation to dolphin behavior. Behavioral data were collected from 686 independent dolphin groups during boat-based surveys conducted between February 2002 and January 2005. Foraging (46.7%) and social (7.2%) were the most and least frequently observed behaviors, respectively. Travel (28.9%), mill (9.5%), and rest (7.7%) accounted for the remainder of the activity budget. Behavior varied seasonally, with the highest proportion of foraging and resting groups observed during the spring and autumn, respectively. Behavior also varied with water depth, with foraging animals observed in the deepest and resting groups recorded in the shallowest regions of the Hauraki Gulf. A correlation between group size and behavior was evident, although behavior did not vary with the composition of dolphin groups. Resting, milling, and socializing animals were more frequently observed in smaller group sizes. Foraging behavior was prevalent in both small and large group sizes, suggesting foraging plasticity exists within this population. Behavior differed between single- and multispecies groups, with foraging more frequent in multispecies groups. Resting, milling, or socializing was rarely observed in the presence of any associated species, indicating the primary mechanism for association is likely prey related.     

Dusky dolphin (Lagenorhynchus obscurus) social structure characterized by social fluidity and preferred companions

Many coastal delphinids exhibit social structures with a high degree of fission‐fusion dynamics. However, little is known about fission‐fusion dynamics in semipelagic delphinids such as dusky dolphins (Lagenorhynchus obscurus). We analyzed dusky dolphin social structure in a winter foraging habitat in New Zealand. We examined the population‐level societal attributes of preferred/avoided companions, behaviorally specific preferred/avoided companions, and simple ratio (SR) association index strength and distribution and the dyad‐level societal attribute of temporal patterning of associations. We identified 741 individuals; 99 met inclusion criteria for analysis. Long‐term and short‐term preferred/avoided companions were present in the pooled (6 yr) and annual samples. Individuals were observed to form long‐term but not short‐term preferred/avoided companions during all behavioral states. Mean and maximum SRs were 0.03 ± 0.01 SD and 0.40 ± 0.20 SD, respectively. Temporal analysis indicated that individuals associated preferentially throughout the study period. Dusky dolphins exhibited high social fluidity, as indicated by many weak and few strong associations. However, there was stability as individuals were observed to form behaviorally specific preferred/avoided companions and associate preferentially throughout the 6 yr period. Dusky dolphins thus display a dynamic social structure where overall low levels of bonding are juxtaposed against a subset of the population that forms strong bonds.     

Individual foraging site fidelity in lactating New Zealand fur seals: Continental shelf vs. oceanic habitats

Wide‐ranging marine central place foragers often exhibit foraging site fidelity to oceanographic features over differing spatial scales (i.e., localized coastal upwellings and oceanic fronts). Few studies have tested how the degree of site fidelity to foraging areas varies in relation to the type of ocean features used. In order to determine how foraging site fidelity varied between continental shelf and oceanic foraging habitats, 31 lactating New Zealand fur seals (Arctocephalus australis forsteri 1 ) were satellite tracked over consecutive foraging trips (14–108 d). Thirty‐seven foraging trips were recorded from 11 females that foraged on the continental shelf, in a region associated with a coastal upwelling, while 65 foraging trips were recorded from 20 females that foraged in oceanic waters. There were no significant differences in the mean bearings (to maximum distance) of individual's consecutive foraging trips, suggesting individual fidelity to foraging areas. However, overlap in area and time spent in area varied considerably between continental shelf and oceanic foragers. Females that foraged on the continental shelf had significantly greater overlap in consecutive foraging trips when compared to females that foraged in oceanic waters (overlap in 5 × 5 km grid cells visited on consecutive trips 55.9%± 20.4% and 13.4%± 7.6%, respectively). Females that foraged on the continental shelf also spent significantly more time within the same grid cell than females that foraged in oceanic waters (maximum time spent in 5 × 5 km grid cells: 14%± 5% and 4%± 2%, respectively). This comparatively high foraging site fidelity may reflect the concentration of productivity associated with a coastal upwelling system, the Bonney Upwelling. Lower foraging site fidelity recorded by seals that foraged in oceanic waters implies a lower density/larger scale habitat, where prey are more dispersed or less predictable at fine scales, when compared to the continental shelf region.     

Environmental and social influences on the genetic structure of bottlenose dolphins (<Emphasis Type="Italic">Tursiops aduncus</Emphasis>) in Southeastern Australia

Determining genetic connectivity of bottlenose dolphin communities helps identify evolutionary mechanisms, such as environmental and social factors, that interact to shape dispersal in highly social marine mammals. Here, we expand on a localized study that found marked genetic differentiation among resident dolphins (Tursiops aduncus) in the Port Stephens embayment and adjacent coastal communities, to include four additional communities inhabiting different environment types along the New South Wales coast, Southeastern Australia. Analysis of the mitochondrial DNA control region and seven microsatellite loci suggest the nine communities may have originated from a single ancestral population that progressively colonised the coast in a southward direction. Gene flow among communities was predominately governed by habitat type. The two enclosed embayments showed the highest level of genetic differentiation from other communities, while genetic differentiation among coastal and open embayment communities generally followed a pattern of isolation by distance. Directional bias in recent migration rates was evident, with the centrally located Hunter coast communities consisting of individuals with mixed ancestry from the Northern, Southern and Port Stephens communities. Emigration from Port Stephens was substantially higher than in the opposite direction, indicating there may be social barriers to dispersal created by Port Stephens dolphins. Our results suggest that the scale of connectivity of bottlenose dolphin communities inhabiting heterogeneous environments is likely to be affected by local habitat adaptation. This has important implications for the management of communities exposed to increasing levels of anthropogenic disturbances, such as the intensive commercial dolphin-watching industry operating in Port Stephens.     

Dolphin sympatric ecology

Interspecific associations between two or more species of the family Delphinidae have been reported by many scientists, but the sympatric ecology of such dolphin associations has not been studied in great detail. A few field investigations have been conducted on this subject in different parts of the world on species such as bottlenose dolphins (Tursiops spp.), short-beaked common dolphins (Delphinus delphis), and killer whales (Orcinus orca). Sympatric dolphins seem to use different strategies to co-exist when resources appear to be limited, including dietary divergence (different prey preference, slightly diverse diet, different feeding time) and/or different habitat use (shallow versus deep waters, flat areas versus submarine canyons and escarpments, different travel routes). This paper presents a review of some well-studied dolphin species found in sympatry and discusses the nature of habitat and resource partitioning as well as studies on aggressive behaviour displayed by species living in the same habitat.     

The structure of a bottlenose dolphin society is coupled to a unique foraging cooperation with artisanal fishermen

Diverse and localized foraging behaviours have been reported in isolated populations of many animal species around the world. In Laguna, southern Brazil, a subset of resident bottlenose dolphins (Tursiops truncatus) uses a foraging tactic involving cooperative interactions with local, beach-casting fishermen. We used individual photo-identification data to assess whether cooperative and non-cooperative dolphins were socially segregated. The social structure of the population was found to be a fission-fusion system with few non-random associations, typical for this species. However, association values were greater among cooperative dolphins than among non-cooperative dolphins or between dolphins from different foraging classes. Furthermore, the dolphin social network was divided into three modules, clustering individuals that shared or lacked the cooperative foraging tactic. Space-use patterns were not sufficient to explain this partitioning, indicating a behavioural factor. The segregation of dolphins using different foraging tactics could result from foraging behaviour driving social structure, while the closer association between dolphins engaged in the cooperation could facilitate the transmission and learning of this behavioural trait from conspecifics. This unique case of a dolphin-human interaction represents a valuable opportunity to explore hypotheses on the role of social learning in wild cetaceans.     

Area utilization patterns of humpback dolphins (Sousa plumbea) in Richards Bay, KwaZulu-Natal, South Africa

Geographically referenced data on humpback dolphin (Sousa plumbea) distribution and behaviour were collected in Richards Bay, South Africa, between 1998 and 2006. Utilization distributions presented a clear pattern in the distribution of dolphin activities and use of various locations within the study area. The 50 % kernel density estimate (core area) for foraging/feeding (2.1 km²) was clustered around the harbour mouth (including the shark net installation). The core areas for resting, socialising and travelling were more widespread (>2.95 km²). A mixed effects model indicated that location (longitude and latitude), distance from shore, year and group size are important variables in predicting foraging/feeding behaviour as opposed to other behaviours. The resting core was found in the southern part of study area and socialising was less clustered. This indicates preferential use of certain areas for specific behaviours. The overlap of foraging/feeding areas with stationary fishing gear (shark nets) and boat traffic are a major concern due to the risk of human-induced incidental mortalities. Any future alteration of the coastal area of Richards Bay, particularly development in the harbour, should be considered carefully, as further intrusion into areas critical to humpback dolphins, such as their foraging grounds, will inevitably carry negative implications for this already severely impacted population.     

“Turtle watching” conservation guidelines: green turtle (<Emphasis Type="Italic">Chelonia mydas</Emphasis>) tourism in nearshore coastal environments

We propose a conservational opportunity for humans to ‘use’ the green turtle (Chelonia mydas) in a non-consumptive manner. Although the concept of a social safe-minimum standard analysis, as applied to the sustainability of tourism-dependent turtle watching, has focused on beach-nesting habitats, other tourist activities like diving and snorkelling also occur in shallow coastal habitats frequented by juvenile and adult turtles. When integrated over time, at a specific location, such tourism activities may compromise turtle physiology in a manner that limits conservation goals for the species and hence the tourism. We identify research insights that can be used to achieve a creatively managed tourism—one that allows tourists to observe turtles in their natural coastal habitat in a manner that is commensurate with functional turtle conservation. We propose management options loosely based on whale-watching: i.e. voluntary and/or mandatory regulations based on home-range studies that identify localized temporal and spatial patterns of habitat use exhibited by turtles. We recommend temporally- and spatially-dynamic stratified-random-design tours that exclude critical local (small-scale) habitat and include less-critical habitat on a randomized rotational basis. Practical guidelines for tour operators that are founded on turtle habitat-occupancy patterns may ensure expanded life-history conservation measures and sustainable turtle-watching tourism.     

Evidence for male dispersal along the coasts but no migration in pelagic waters in dusky dolphins (Lagenorhynchus obscurus)

Using nine nuclear species-specific microsatellite loci and two mitochondrial gene fragments (cytochrome b and control region), we investigated the processes that have shaped the geographical distribution of genetic diversity exhibited by contemporary dusky dolphin (Lagenorhynchus obscurus) populations. A total of 221 individuals from four locations (Peru, Argentina, southern Africa, and New Zealand) were assayed, covering most of the species’ distribution range. Although our analyses identify a general demographic decline in the Peruvian dusky dolphin stock (recently affected by high natural and human-induced mortality levels), comparison between the different molecular markers hint at an ancient bottleneck that predates recent El Niño oscillations and human exploitation. Moreover, we find evidence of a difference in dispersal behaviour of dusky dolphins along the South American coast and across the Atlantic. While data in Peruvian and Argentine waters are best explained by male-specific gene flow between these two populations, our analyses suggest that dusky dolphins from Argentina and southern Africa recently separated from an ancestral Atlantic population and, since then, diverged without considerable gene flow. The inclusion of a few New Zealand samples further confirms the low levels of genetic differentiation among most dusky dolphin populations. Only the Peruvian dusky dolphin stock is highly differentiated, especially at mitochondrial loci, suggesting that major fluctuations in its population size have led to an increased rate of genetic drift.     

Efficacy of voluntary mitigation in reducing harbor seal disturbance

Marine and coastal tourism has rapidly expanded worldwide in the past 2 decades, often occurring in once secluded habitats. In Alaska, tourism near tidewater glaciers has attracted millions of visitors and increased the presence of ships, tour vessels, and coastal development. Although sustainable tourism, resulting from balanced effects on wildlife and client satisfaction, is a goal of most tourism operators, it is not always achieved. Voluntary compliance with viewing guidelines and codes of conduct have been encouraged, but few assessments have the longitudinal scope to evaluate long-term changes in impacts on wildlife and the ability of vessel operators and kayak guides to sustain lower impact operating practices over time. This study assessed vessel and kayak visitation and resulting impacts on harbor seals in the Kenai Fjords National Park, southcentral Alaska. We obtained observations from 2002 to 2011, using remotely controlled video cameras located near Aialik and Pedersen Glaciers in the Kenai Fjords National Park. Overall, disturbance was associated with 5.1% of vessel sightings, 28% of vessel interactions (vessel observed within approx. 300 m of seals), 11.5% of kayak sightings, and 61% of kayak interactions. Results demonstrated that voluntary changes in operations significantly reduced vessel and kayak disturbance of seals by 60–80%. Even with prior establishment of operating guidelines, tour vessel captains were able to further reduce their effect on wildlife with more careful operations. Rapid growth of guided kayak excursions that occurred during this study caused greater disturbance to seals than motorized vessels but guide trainings helped reduce disturbances. Diminished impacts of motor vessels and kayakers persisted across years although effects of kayaks were less consistent than motor vessels, which reflected greater variability in inter-annual spatial use patterns by kayakers. Long-term monitoring, including assessments of wildlife responses to vessel and kayak operations, combined with 2-way communication with vessel operators and guides, enhanced the effectiveness of mitigation and facilitated adaptive adjustments to mitigation protocols over time. © 2013 The Wildlife Society.