Habitat preference and spatial distribution of Guiana dolphins (Sotalia guianensis) in Norte Bay, southern Brazil, was studied from 2001 to 2005. Boat surveys (N = 91) were made to evaluate the spatial distribution of the dolphins. Seven habitat variables were integrated into a geographical information system, and habitat preference was tested using the ‘Neu method’ and a habitat index. The Guiana dolphins did not use all habitat types in the same proportion as were available. Areas used more intensively included, in order of importance: (1) areas with a steep sloping sea-floor; (2) areas further from urban areas; (3) areas further from mangroves; (4) areas near the mouth of the bay; (5) shallow water areas; (6) areas of clayey-silt sediments; and (7) areas close to shore. From 2001 to 2005 there was a shift in spatial distribution and habitat use by the dolphins. The low frequency of use of areas close to urban encroachment and its related impacts to the marine environment raises concern about the coastal habitat destruction. The Guiana dolphin may be considered a habitat specialist, despite its wide latitudinal distribution in the western Atlantic Ocean. The ecological niche of the species may be defined by a narrow strip of shallow coastal waters (mostly < 30 m) bordering the coastline. The shift in the spatial use was probably linked with changes in the abundance of important prey of the species and possibly was caused by the collapse of a fish stock in the study area region. Different habitats may favour different assemblages of prey and consequently different foraging strategies by the dolphins. Human-related habitat alterations throughout the range of this species are likely to affect dolphins' ecology in many ways and, thus, must be evaluated and mitigated to conserve their critical habitats.

To determine the group structure of Sotalia guianensis on the coast of Paraná State, two bays, Baía de Paranaguá and Baía de Guaratuba, were surveyed between March 1999 and February 2000 and between July 2002 and June 2003 respectively. The heterogeneity of the studied areas was considered a relevant factor, therefore these areas were sectored and each sector was investigated independently. The surveys were carried out through boat line transects and all the animals were registered, even those localized between two transects. The records were taken for the quantity of groups as well as for the amount of individuals in each group and, whenever possible, the individuals were classified as calves or adults. The data were treated both separately and comparatively between the two bays and amongst the sectors of each bay. In Baía de Paranaguá, 735 individuals were registered, divided into 253 groups which varied from 2 to 37 individuals for an average of 2.9 individuals per group. Most of the groups presented a family formation (59.29%) and were observed during the morning. The individuals that were clearly identified as calves represented 24% of the total (176 individuals), adults 55% (405 individuals) and 21% (154 individuals) were impossible to determine. In Baía de Guaratuba, only 32 S. guianensis individuals were observed and distributed into 14 groups for an average of 2.13 individuals per group. These groups varied from 2 to 6 individuals mostly in family formations (50%). The same quantity of individuals and groups was observed during different periods of the day. Of the 32 sampled individuals, 25 (78%) were adults, only one was a calf (3%) and 6 (19%) were undetermined.

Sources of International Law — Customary International Law — Acquiescence as Evidence of International Law.

Bays — Delimitation of — Base-Line — Ten-Miles Rule.

Territorial Waters — Measurement of — Base Line — Sinuosities of the Coast — General Direction of the Coast — The Nature of the Coast and the Determination of the Base Line — Bays — Historic Waters — Ten-Mile Rule — International Character of Delimitation of Territorial Waters — Criteria of Delimitation — Evidence of Existing Practice — Application of the System of Straight Lines — Acquiescence of States Affected by Unilateral Measures of Delimitation — Application of the System of Straight Lines to Specific Areas.

Bays — Territorial Waters — Limits of — Fisheries — Iceland — Statement of German Ministry of Defence — How Far Binding Upon German Courts.

Bays — Territoriality of — Base Line of Territorial Waters.

Territorial Waters — Limits of — Base Line — Territoriality of Bays.

Bays — Extent of — Penobscot Bay of the State of Maine.

Territorial Waters — Extent of — Islands — Protective Jurisdiction — Bays — Penobscot Bay of the State of Maine.

Territorial Waters — Limits of — Bays — Base Line.

Bays — Base Line — Santa Monica Bay in California.

State Territory — Bays — Base Line of — Santa Monica Bay in California — Territorial Waters — Extent of.

Bays — Extent of — Base Line of Territorial Waters — Law of Norway — Fiords.

Territorial Waters — Extent of — Base Line — Bays — Fiords — The Law of Norway.

Bays — Measurement of — The Monterey Bay of California

Bays — Measurement of Maritime Belt.

Territorial Waters — Breadth of the Maritime Belt — Claim by Swedish Government — Fisheries.

Bays — Non-Territorial — The Bristol Channel — Territorial and Non-Territorial Bays.