Harbour porpoise (Phocoena phocoena) are the most abundant cetacean in UK waters, and are likely to be affected by a variety of marine industries and activities. This research uses data collected by acoustic recorders (C-PODs) and aerial video surveys to investigate patterns in porpoise detection. The findings can be split into five key themes, and are used to support the development of spatial management and survey recommendations. 1. Porpoise detection changes based on time of day in different habitats, indicating possible differences in diel habitat use and highlighting potential issues with visual or video data collection methods for assessing distribution. 2. Porpoise exhibit seasonal shifts in detection, yet year-round data are often lacking, therefore seasonal changes in distribution are often unknown. 3. The highest proportions of buzzes (associated with foraging) are not detected in areas with the highest relative density of porpoise. I propose that porpoise use different foraging strategies in different habitats which are not equally detectable by acoustic recorders. 4. Porpoise distribution may be influenced by the distribution of perceived risk from predator / competitor species (dolphins). Temporal partitioning of sites may arise either from porpoise actively avoiding times when bottlenose dolphins are expected to be present, or from porpoise and bottlenose preferences for different environmental conditions. 5. The choice of spatial modelling method can influence the fine-scale predictions of areas with the highest density. Improving our understanding of top and mesopredator ecology is informative for management strategies. Each of the points raised above should be considered when determining management strategies to minimise the impact from fisheries, offshore developments and other industrial activities on harbour porpoise.

Incidental catch (bycatch) in fisheries is one of the major threats to marine mammal populations worldwide. The harbour porpoise (Phocoena phocoena, Linneaus 1758) is one of the most common cetaceans in northern Europe. Previous studies have reported high bycatch numbers of harbour porpoises in gillnet fishing operations in the North Sea and Skagerrak Sea. With the aim of disentangling the driving factors behind bycatch of harbour porpoises, I looked at the relationship between occurrence of harbour porpoise bycatch and properties of fishery and porpoise density. Parameters of fishing effort, gear characteristics and operations of 951 sets of strings of cod and pollack bottom set gillnets were collected by an on-board observer programme in the Swedish Skagerrak and Kattegat Seas during 1995-1997. Porpoise density data was generated from satellite tracking locations of 116 individuals from 1997 to 2016. Generalised linear models with binomial distribution were applied to identify the relationships between the occurrence of porpoise bycatch and seven explanatory variables extracted as soak time, string length, net height, mesh size, net bagginess, water depth and porpoise density. During the observer programme, a total of 21 porpoises were bycaught during 10,174 km*h of observed fishing effort. The total bycatch was estimated to be 2.6% of the population abundance at that time, i.e. above the maximum sustainable total anthropogenic removal (1.7%). Soak time, string length and water depth were identified to be positively related to bycatch occurrence. The findings provide guidance for bycatch mitigation measures in terms of adjusting fishing operations, improving gear and establishing separate management units. Modelling can be used to predict possible spatio-temporal high-risk hot spots for harbour porpoise as well as other marine-living species to optimise future monitoring efforts.

A prevalence of 76% and a mean intensity of 42.7 Anisakis simplex was found in harbour porpoises (Phocoena phocoena) (N = 78) by-caught in cod gill nets set by fishers from the Gaspe area in summer 1993. No young-of-the-year porpoises (N = 12) were infected. Prevalence and mean intensity among immature and adult porpoises as well as between sexes and length-classes were not significantly different. Anisakis simplex was present in the three stomach compartments of harbour porpoises. Adult stages were proportionately less abundant in the main and pyloric stomachs than the forestomach. Percent intensity of A. simplex was influenced by maturity of harbour porpoises. Gravid female A. simplex contained up to 818,000 eggs. Egg number was highly correlated with worm uttering volume. Density effects were not demonstrated, possibly due to high variability of egg number, total length, uterine and total worm volume between parasites from each stomach and between stomachs of harbour porpoise.

The harbor porpoise is considered a threatened species in Swedish waters. A full understanding of its ecology and relationship to other species is important when designing effective conservation plans. This thesis aims to investigate the relationships between harbor porpoises and their prey by comparing the acoustic activity patterns of harbor porpoises and the movement patterns of some of their prey species available at Kullaberg, Sweden. For this purpose, the scientific literature of porpoise and fish activity patterns has been reviewed. Results show that harbor porpoises may follow vertically migrating herring, but further studies are needed to confirm this. It is also possible that the activity pattern of porpoises does not follow exactly the movements of a certain species of prey, but that they rather feed upon several species, and therefore change their behavior accordingly throughout the diurnal cycle.

Harbour porpoises (Phocoena phocoena) are the only cetacean residents found year-round in Swedish waters. Since in situ monitoring of cetaceans can be difficult, invasive and often costly, strandings can be used as a cost-effective alternative to continuously collect data on these elusive animals. In this study, spatiotemporal patterns, and their possible underlying causes, of harbour porpoise stranding reports in Swedish waters are investigated over the ten-year period of 2014–2023. When making spatial comparisons, for management purposes, the ten-year period is divided into two, 2014–2018 and 2019–2023. Data on 854 stranded harbour porpoises were analysed from the coasts of the Skagerrak, Kattegat, and Baltic Seas. Both significant spatial and temporal patterns could be identified, with strandings peaking in July to September and with hotspots occurring along most of the Swedish west coast, with the most frequent hotspots located around Öresund and especially the area around Kullen peninsula. The spatial patterns of strandings found in this study reflect data on porpoise abundance, prey abundance, and gillnet fisheries effort. The latter is known to be one of the primary causes of porpoise mortality. Furthermore, the coverage of the Swedish stranding network is analysed. While coverage of the stranding network overall has increased over the period, some areas still lack sufficient coverage, including the coast of Falkenberg, southern Gothenburg, northern Halmstad and certain areas around Lommabukten, north of Malmö. With this, we conclude that harbour porpoise strandings in Sweden show distinct spatiotemporal patterns that can be used as baselines for management and monitoring of these small cetaceans.

No description available.

Since the 1950s, more than 6 million dolphins have died as by-catch in the American yellowfin tuna fishery. These deaths were not caused by accidental incidents between fishermen and dolphins but resulted from a method of fishing that purposefully targeted these animals in order to catch yellowfin tuna. Referred to as “fishing on porpoise,” this technique remained an industry secret for decades. By the early 1970s, however, dolphin by-catch had become a major environmental issue in the United States, thanks to the work of William F. Perrin. In the following years, politicians, scientists, environmentalists, and members of the tuna industry struggled with how best to resolve the problem. While the debates that arose from the “tuna-porpoise controversy” helped to dramatically reduce dolphin by-catch, these solutions did not come easily. This thesis looks to bring this forgotten moment in American environmental history to the historical forefront by exploring the origins and early years of the tuna-porpoise controversy. By examining this period, this thesis will show why fishermen first used dolphins to catch tuna in the 1950s, how and why dolphin by-catch became such a major environmental issue in the 1970s, and what various groups and individuals did to ameliorate the problem during the period. / Graduate

Thesis (Ph. D.)--University of Washington, 1998. / Vita. Includes bibliographical references (leaves [235]-251).

Thesis (M.Sc.)--Memorial University of Newfoundland, 1997. / Bibliography: leaves 135-147.

The aim of this report was to establish what category the harbour porpoise is listed as on the Swedish national redlist as well as analyze what potential sub-criteria the species fulfills besides criteria already established. The aim was also to evaluate the willingness to pay for conservation of the harbour porpoise for the first time and make a comparison of the willingness to pay between geographic places where the harbour porpoise is currently existing and where it is not. The subpopulation of the harbour porpoise in Skagerrak-Kattegat is listed as vulnerable (VU) on the national redlist and the subpopulation in the Baltic sea is listed as critically endangered (CR). Actions and precautions which have been made for conservation and protection of the harbour porpoises in Swedish waters are new Swedish laws and law proposals as well as formations of organizations such as ASCOBANS and further research. The results from the survey showed that the mean of the single time payment sum those questioned were prepared to pay to retain the porpoises at a stable population level was 273 SEK. Geographically the study showed no significant difference in geographic position and where the harbour porpoise exists but showed that the inhabitants of the south-east coast were willing to pay about half the sum, 165 SEK, of the mean sum that the north-east coast were willing to pay, 335 SEK. The results regarding the populations’ conjecture of historical threats and threats nowadays showed a significant difference from reality. Overfishing of prey had the highest amount of answers as a threat both historically and nowadays. Bycatch, which is accepted as todays biggest threat by researchers and organizations, came third place in the results from the survey study with a percentage of 14.5 %.