Lisa T. Ballance

The abundance of cetaceans in the eastern tropical Pacific Ocean (ETP) is estimated using spatial/temporal density modeling and conventional line‐transect approaches. Line‐transect data are analyzed from 10 ship‐based visual sighting surveys from 1986 to 2006 that include 281,000 km of survey effort in a 19.4 million km ² study area. Three generalized additive density models are evaluated for each of 26 taxonomic categories (e.g., species, U.S. Marine Mammal Protection Act stocks, or genera), and the best‐fit model is used to estimate abundance. The three models include varying levels of complexity in spatial (latitude, longitude, and distance from the coast) and temporal (survey years) predictors. Group‐size, Beaufort state, and availability bias corrections are applied, which results in abundance estimates that are typically 2–6 times greater than those from previous analyses of the same data. After correcting for these biases, conventional design‐based estimates are similar to model‐based estimates. Our higher abundance estimates have significant implications for interpretating the status of depleted stocks of dolphins that have been impacted by the ETP tuna purse‐seine fishery. Additionally, the spatial/temporal models provide new insights into how these species are distributed in the ETP and how those distributions have changed through time.

Vessel-cetacean collisions pose a major and growing threat to whale populations worldwide, yet management responses remain limited. We present an integrated, spatially explicit decision-support framework for quantifying and managing collision risk within Marine Spatial Planning process (MSP). The framework is applied to Mexico's Central-South Pacific (CSP), where critical habitat for humpback and other rorqual whales overlaps with the Eastern Pacific shipping corridor. Collision risk assessment is an immediate priority, as CSP hosts five major cargo ports and is undergoing a major government-led maritime infrastructure expansion.,The framework integrates vessel-cetacean encounter rate modeling within Decision Making under Deep Uncertainty (DMDU). Monte Carlo simulation was implemented to characterize collision risk across stakeholder preference scenarios. Results were robust across these preferences and supported targeted speed restrictions. Two critical speed thresholds were identified: 24 km∙h-1 (13 kn) and 33 km∙h-1 (18 kn). A 30% speed reduction within this interval decreased the 10-year cumulative lethal collision probability by up to 80%. Maximum coverage geospatial analysis delineated six vessel speed zones around four major ports, minimizing omission errors while meeting maritime operational constraint,By rendering structural commitments, definitions, and assumptions explicit and verifiable through axiomatization, the framework produces analytically defensible management measures suited to the deliberative requirements of MSP. The approach is generalizable across regions and taxa.

Climate-induced changes in ocean conditions are likely to affect species habitat use across current management boundaries (e.g., marine protected areas). Therefore, it is important to identify potential future risks that may reduce the effectiveness of fixed boundaries or cause negative interactions between wildlife and human ocean-use sectors. Here, we used presence and absence records from a compilation of > 132,000 ship-based and aerial at-sea visual survey transect segments collected from 1980-2017 to fit species distribution models (SDMs) for five abundant and ecologically important seabird species in the California Current Ecosystem (CCE), including both resident (common murre, Cassin’s auklet, and rhinoceros auklet) and seasonal migrant (sooty shearwater, black-footed albatross) species with different life-histories. We then projected their daily habitat suitability from 1980-2100 using an ensemble of three dynamically downscaled, high-resolution (0.1°) climate projections for the CCE. We compared long-term changes in both mean conditions and intra-annual (seasonal) variability within four National Marine Sanctuaries and four proposed areas for offshore wind energy development in the CCE. Sea surface temperature, bottom depth, daylength, and biogeographic province were the most important variables, with relative importance being species-specific. Each species displayed a negative relationship with increasing temperatures that was most pronounced in the two auklet species. Accordingly, habitat suitability scores declined across the CCE, most prominently south of Point Conception, emerging from historical variability for all species except sooty shearwater. Despite long-term negative trends in habitat suitability, we identified extensive species-specific seasonal refugia, highlighting potential changes in the intra-annual occurrence of suitable habitat. Our results suggest that perceptions of conservation benefits of marine sanctuaries and potential interactions between seabirds and new ocean-use development could be notably different by 2100, and that many impacts may occur by mid-century. Thus, it is critical to consider future projections of species habitat suitability within marine spatial management and planning processes.

Although Hubbs' beaked whale (Mesoplodon carlhubbsi) was previously known from over 60 strandings on both sides of the North Pacific, it had been identified alive in the wild only once, off Oregon in 1994. In September 2021, we conducted a search effort for beaked whales off the coast of Oregon using a towed hydrophone array and a visual search team. Approximately 350 km off the Columbia River mouth, we detected the vocalizations of an unidentified mesoplodont whale; we stopped our vessel and waited in the area until two unidentified juvenile Mesoplodon surfaced and stayed near our vessel for almost 2 hr. During that time, we took numerous photographs and videos, made behavioral observations, and recorded their vocalizations. The DNA sequence from a biopsy sample identified them as M. carlhubbsi. In this paper, we discuss our biological observations, including color patterning and acquired markings, behavioral observations, and describe for the first time the acoustic characteristics of this species. We confirm that M. carlhubbsi is the source of a previously unidentified acoustic signal known as BW37V, and we update what is known about the at‐sea distribution of this species based on previous recordings and observational records.

Genome sequences can reveal the extent of inbreeding in small populations. Here, we present the first genomic characterization of type D killer whales, a distinctive eco/morphotype with a circumpolar, subantarctic distribution. Effective population size is the lowest estimated from any killer whale genome and indicates a severe population bottleneck. Consequently, type D genomes show among the highest level of inbreeding reported for any mammalian species (F_ROH ≥ 0.65). Detected recombination cross-over events of different haplotypes are up to an order of magnitude rarer than in other killer whale genomes studied to date. Comparison of genomic data from a museum specimen of a type D killer whale that stranded in New Zealand in 1955, with 3 modern genomes from the Cape Horn area, reveals high covariance and identity-by-state of alleles, suggesting these genomic characteristics and demographic history are shared among geographically dispersed social groups within this morphotype. Limitations to the insights gained in this study stem from the nonindependence of the 3 closely related modern genomes, the recent coalescence time of most variation within the genomes, and the nonequilibrium population history which violates the assumptions of many model-based methods. Long-range linkage disequilibrium and extensive runs of homozygosity found in type D genomes provide the potential basis for both the distinctive morphology, and the coupling of genetic barriers to gene flow with other killer whale populations.

Multispecies aggregations of tuna, dolphins, and seabirds are prevalent and conspicuous in the vast waters of the eastern tropical Pacific and form the basis of a commercial fishery for yellowfin tuna (Thunnus albacares) through setting on schools of dolphins, which is among the largest tuna fisheries in the world. Incidental dolphin mortality associated with the development and early years of the fishery was high; by 1993 it was estimated that eastern spinner dolphins (Stenella longirostris orientalis) had been reduced to 44% and northeastern offshore spotted dolphins (S. attenuata attenuata) to 19% of pre-fishery levels. Efforts to reduce this mortality began at the inception of the fishery and comprised a diverse array of approaches: modifications to fishing methods and fishing gear (backdown, Medina panel, high-intensity floodlights, swimmers to disentangle and release dolphins); U.S. legislation (through the U.S. Marine Mammal Protection Act, MMPA, and subsequent amendments); international agreements (including the International Dolphin Conservation Program that established dolphin mortality limits, and the legally binding multilateral Agreement on the International Dolphin Conservation Program); and economic incentives [notably through establishment of the U.S. dolphin-safe label and positive certification by the Marine Stewardship Council (MSC)]. Together, these bycatch mitigation efforts have been remarkably successful; dolphin mortality due to entanglement as recorded by fisheries observers (hereafter, entanglement mortality) has been reduced by > 99%. Despite this, the degree to which dolphin populations have recovered remains unclear. Multiple lines of evidence indicate that individual dolphins experience multiple sets in their lifetimes and although causality has not been established, research suggests that chase and encirclement might have impacts on dolphins in addition to entanglement mortality. These impacts potentially include increased fetal and/or calf mortality, separation of nursing females and their calves, decreased fecundity, increased predation, disruption of mating and other social systems, and ecological disruption. The strong management emphasis on monitoring entanglement mortality, and the infrastructure necessary to support this monitoring (in particular, 100% observer coverage on large purse-seiners) require funding to the extent that other activities, particularly continued surveys to monitor stock status and clarify the potential influence of other effects of the fishery on dolphin populations, are currently inadequately funded.