Preface

There are 130 described species of marine mammals living within the Earth's oceans. These include cetaceans (whales and dolphins), pinnipeds (33 species of aquatic fin-footed mammals, such as fur seals and sea lions), sirenians (sea-cows or sirenians), sea otters (the smallest marine mammals), and polar bears.

This book offers a broad perspective on marine mammal species and populations considered to be most at risk due to human activities. It emphasizes the importance of understanding the essential biology and ecology of marine mammals to assess the correlates and causes of extinction and to implement science-based conservation.

The book contains seven chapters.

Chapter 1: "Introductory Chapter: Marine Mammals of the World"

This chapter discusses different types of marine mammals and their importance to the ecosystem of the world's oceans and food cycles. Additionally, the chapter addresses the threats facing marine mammals and attempts to answer the questions: Why is it important to safeguard marine mammals? Why is marine conservation important? How can we protect marine mammals? Finally, the chapter illustrates global hotspots where marine mammal species are at risk of extinction and examines the geographic distributions of the leading human impacts.

Chapter 2: "Phylogeny and Population Genetic Structure of Minke Whales Worldwide: A Review of Recent Studies"

This chapter reviews the genetic studies on minke whales. The review is organized by topic, e.g., those studies focused on phylogeny and other matters most relevant for taxonomy, and those focused on population genetic structure.

Chapter 3: "Applications of Omics Approaches to Decipher the Impact of Contaminants in Dolphins"

This chapter explains the importance of omic technologies in the field of marine genomics with the advent of omic technologies (genomic, transcriptomic, proteomic, metabolomic, and lipidomic).

Chapter 4: "Typical Changes in Carbon and Nitrogen Stable Isotope Ratios and Mercury Concentration during the Lactation of Marine Mammals"

This chapter deals with lactation in marine mammals.

Chapter 5: "Perspective Chapter: Status of Dolphin in the Maritime Area of Bangladesh"

This chapter discusses dolphin survival rates and causes of movement reduction in Bangladesh. The dreadful conditions of coastal habitats can have major impacts on dolphin population and distribution.

Chapter 6: "Marine Mammals in Syria"

Syrian marine water is one of the least studied areas for cetaceans in the Mediterranean Sea. Lack of basic knowledge such as species composition and habitat makes it impossible to develop effective conservation measures. The survey in this chapter was carried out along the Syrian coasts.

Chapter 7: "How Do Whales See?"

This chapter studies the eyes of two whales: *Balaenoptera physalus* and *B. borealis*. It presents anatomical, histological, immunohistochemical, and ultrastructural studies of the eyes of both types of whales.

The book is characterized by precision and care and ensures that there aren't any errors – irrespective of how small – within the scales, colorations, and details of the drawings. Fortunately (or otherwise), many of these rare species are still unknown to most people – and may remain unknown forever.

I gratefully acknowledge the help provided by all authors that have contributed to the publication of this volume. I am also thankful to IntechOpen for initiating this project.

> **Hussein Abdelhay Essayed Kaoud** Professor, Faculty of Veterinary Medicine, Cairo University,

> > Giza, Egypt

**Chapter 1**

**1. Introduction**

**1.1 Definition**

Introductory Chapter: Marine

Marine mammals are, in short, catalytic species. Thus, knowledge of areas that are important for them will facilitate the balancing of human uses of the ocean with the

Marine mammals are highly consumed animals of marine creatures production at the different levels specially utmost trophic type from initial production as sea-cows or sirenians, are an order of fully aquatic, herbivorous mammals) to predatory fish and some other types of marine mammals, such as the polar bear, some whales, and dolphins.

Because of their large body size and abundance, they are thought to own a serious

In marine ecosystems, marine mammals play an important role in balancing and

1.They provide a context to regulate and to judge the potential influence of their

3.They impact or influence the variation in prey populations that harvesting by

4.They regulate the dynamics of marine mammals [1] during environmental

Human activities represent a big threat to words marine mammals. These activities comprise "Bycatch" in marine media, collision with vessels, reduction of prey resources, and climatic changes on the planet. The danger of water pollution, excessive hunting or fish harvesting, diseases, and habitat destroying or degradation and loss.

influence on the structure and performance of some marine communities.

regulating the dynamics of production in the ecosystems as the following:

2.They regulate and balance the structure of marine populations.

Mammals of the World

*Hussein Abdelhay Essayed Kaoud*

imperative of conserving marine biodiversity.

**2. Role of marine mammals in ecosystems**

predation on prey populations.

**3. Threats due to human activities**

humans.

changes.
