Phillip J. Clapham

The IWC Scientific Publications series was established to make available in published, peer-reviewed form, scientific papers that have contributed to the work carried out by the IWC Scientific Committee. The IWC Scientific Committee provides scientific advice on marine mammal species and stocks in the North Atlantic in response to requests forwarded to it by the Council of IWC. Most volumes are therefore organised around a theme, reflecting the nature of the original request for advice.

Photographic and genetic studies have revealed the complex population structure of migratory large whales. Most research and management are geographically based, focusing on either wintering or summering areas, which in most cases fails to capture this complexity. We use examples from humpback whales (Megaptera novaeangliae) and gray whales (Eschrichtius robustus) to illustrate the concept of migratory herds, defined here as conspecific whales that migrate between the same wintering and feeding ground. In cases where individuals show strong fidelity to both feeding and wintering grounds, and therefore to a herd, dispersal between herds can be low enough to render them as demographically independent populations, where population dynamics are determined more by net internal recruitment (births minus deaths) than by immigration from outside sources. In these cases, the migratory whale herd is the appropriate unit to conserve under the ecological paradigm that focuses on groups united by demographic forces. We suggest that when addressing questions focused on ecological timescales for whale species with strong fidelity to migratory destinations, the migratory whale herd is a better initial working hypothesis rather than one based on geographically defined strata.

Introduction: The yellow-bellied sea snake (Hydrophis platurus, formerly Pelamis platurus) is known to occur along the Pacific coast of Central America. However, there are no marine records of this species off the coast of Nicaragua. Objective: Report the first in situ marine observations of the yellow-bellied sea snake observed on three occasions in 2020 during cetacean surveys off the southwestern Pacific coast of Nicaragua. Methods: During the sightings, photographs were taken which allowed the identification of the species based on morphology. Sea surface temperature, sea state, and distance to the coast are presented as descriptors of the habitat of the records. Results: Three field observations of yellow-bellied sea snakes were recorded on separate occasions. Sightings occurred within 30 km of each other and 3.3 km from the coast. Average sea surface temperature was 26.6 °C with low swell and sea state. Conclusions: The present information offers new knowledge about the presence of the yellow-bellied sea snake on the Pacific coast of Central America, contributing to the biodiversity record in Nicaragua. Introducción: La serpiente marina de vientre amarillo (Hydrophis platurus, anteriormente Pelamis platurus) se encuentra distribuida a lo largo de la costa del Pacífico de América Central. Sin embargo, no existe registros in situ sobre esta especie en la costa del Pacífico de Nicaragua. Objetivo: Reportar las primeras observaciones in situ de la serpiente marina de vientre amarillo en tres ocasiones durante el 2020 frente a la costa suroeste del Pacífico de Nicaragua. Métodos: Los registros se realizaron de manera oportunista durante avistamientos de cetáceos en la zona. Las serpientes marinas fueron fotografiadas para su identificación a nivel de especie en base a su morfología. Durante cada avistamiento se registró la temperatura de la superficie del mar, el estado del mar y la distancia a la costa como descriptores del hábitat. Resultados: Se registraron tres serpientes marinas de vientre amarillo en distintas ocasiones. Los avistamientos ocurrieron a menos de 30 km entre sí y a 3.3 km de la costa. La temperatura media de la superficie del mar fue de 26.6° C con oleaje y estado de la mar bajos. Conclusiones: El presente estudio brinda nuevo conocimiento sobre la distribución de la serpiente de vientre amarillo en la costa del Pacífico de Centroamérica, contribuyendo al registro de biodiversidad en Nicaragua.

24. Whales, Whaling, And Ecosystems In The North Atlantic Ocean was published in Whales, Whaling, and Ocean Ecosystems on page 314.

The recovery of whale populations from centuries of exploitation will have important management and ecological implications due to greater exposure to anthropogenic activities and increasing prey consumption. Here, a Bayesian population model integrates catch data, estimates of abundance, and information on genetics and biology to assess the recovery of western South Atlantic (WSA) humpback whales (Megaptera novaeangliae). Modelling scenarios evaluated the sensitivity of model outputs resulting from the use of different data, different model assumptions and uncertainty in catch allocation and in accounting for whales killed but not landed. A long period of exploitation drove WSA humpback whales to the brink of extinction. They declined from nearly 27 000 (95% PI = 22 800–33 000) individuals in 1830 to only 450 (95% PI = 200–1400) whales in the mid-1950s. Protection led to a strong recovery and the current population is estimated to be at 93% (95% PI = 73–100%) of its pre-exploitation size. The recovery of WSA humpback whales may result in large removals of their primary prey, the Antarctic krill (Euphausia superba), and has the potential to modify the community structure in their feeding grounds. Continued monitoring is needed to understand how these whales will respond to modern threats and to climate-driven changes to their habitats.

The demography of baleen whales and their prey during the past 30 thousand years was assessed to understand the effects of past rapid global warming on marine ecosystems. Mitochondrial and genome-wide DNA sequence variation in eight baleen whale and seven prey species revealed strong, ocean-wide demographic changes that were correlated with changes in global temperatures and regional oceanographic conditions. In the Southern Ocean baleen whale and prey abundance increased exponentially and in apparent synchrony, whereas changes in abundance varied among species in the more heterogeneous North Atlantic Ocean. The estimated changes in whale abundance correlated with increases in the abundance of prey likely driven by reductions in sea-ice cover and an overall increase in primary production. However, the specific regional oceanographic environment, trophic interactions and species ecology also appeared to play an important role. Somewhat surprisingly the abundance of baleen whales and prey continued to increase for several thousand years after global temperatures stabilized. These findings warn of the potential for dramatic, long-term effects of current climate changes on the marine ecosystem. One Sentence Summary: The effects of past global warming on marine ecosystems were drastic, system-wide and long-lasting.

Falsification of reports on Japanese catches of sperm whales (Physeter macrocephalus) is known to have occurred at both land whaling stations and in North Pacific factory fleets. Here, we conduct an analysis of pelagic sperm whale catches in the Southern Hemisphere: we compare true Soviet length data from theYuri Dolgorukiyfactory fleet during 1960–1975 to data for the same period reported to the International Whaling Commission (IWC) by Japan. Prior to implementation of the International Observer Scheme (IOS) in 1972, the Soviet fleet killed 5536 females, of which only 153 (2.8%) were at or above the minimum legal length of 11.6 m. During the same period, Japan killed 5799 females and reported that 5686 (98.5%) were of legal size, with 88.5% of the entire length distribution reported as being between 11.6 and 12.0 m. This unrealistic distribution, together with the fact that Japanese fleets were supposedly able to catch 37 times the number of legal-sized females as the Soviet fleet, indicates extensive falsification of catch data by Japan. Further evidence of misreporting is that females >11.5 m dropped to 9.1% of the Japanese catch after 1971, when the IOS made cheating much more difficult. That 99.6% of 10 433 males in the pre-IOS catch were also reported to be of legal size, indicates that illegal catches were not confined to females. We caution that the Japanese sperm whale data in the IWC Catch Database are unreliable and should not be used in population assessments. The ease with which illegal catches were apparently made underscores the past failures of the IWC to effectively regulate whaling.