Preface

Cartilaginous fishes or Chondrichthyans are an ancient group that appeared around 500 million years, even before the appearance of bony fish. Their current representatives are sharks, rays, and chimeras, hereafter referred to as 'sharks'. Some primitive forms of sharks are still present. These animals have been able to survive and overcome five mass extinctions since their initial appearance. They play a key role in maintaining the balance of marine ecosystems.

Nowadays, sharks are facing a worldwide extinction crisis; since 1970, the global abundance of oceanic sharks and rays has declined by 71%, owing to an 18-fold increase in relative fishing pressure. This depletion has increased the global extinction risk to the point at which three-quarters of the species comprising this functionally important assemblage are threatened with extinction. The International Union for the Conservation of Nature (IUCN), recognized at the international level to provide scientific advice on the conservation status of living species, confirm through its "Red List of Threatened Species" that a high percentage of sharks are threatened and many species are data deficient (i.e., their biology and ecology are unknown). Sharks face many challenges, such as habitat losses, pollution, climate changes, and so on, but fishing pressure seems to be the most critical.

Because the disappearance of sharks threatens the oceans and humanity, scientists, decision-makers, NGOs, and other stakeholders require improved knowledge of shark species and how to protect them. This book presents data on sharks' biology and ecology and discusses the impact of threats and how to reduce them. It is designed to bring awareness to the plight of sharks and their conservation. It is divided into three sections on "Ecology and Life History," "Sharks Fisheries," and "Management and Conservation Options."

Chapters 1 and 2 provide information on shark ecology, life history, and taxonomy. Chapters 3 and 4 describe shark fisheries (fishing gear, landing statistics, etc.) and their negative impact on shark populations. Chapter 5 focuses on the current status of cartilaginous fishes in the Mediterranean Sea, which is similar to other marine areas, and discusses progress on conservation measures and actions taken mainly through regional plans by regional fisheries management organizations (RFMOs) and nongovernmental organizations (NGOs).

Since the future of marine biodiversity and sustainable fishery majorly depends on elasmobranchs, more successful conservation of this fish group should be ensured, and urgent awareness is needed focusing mainly on the following priorities:

• Increase training and awareness of fishermen and controllers of fisheries on protected species and develop an effective control of fisheries

• Improve shark conservation by:

reducing bycatch mainly through species release

mapping and monitoring of critical habitats


To develop this research field, experts should focus on (1) biological parameters, (2) knowledge of fisheries, (3) valuable and available statistics, (4) taxonomy and shared stocks, (5) studies on migration and exchange between populations, and (6) choosing better evaluation methods.

I would like to thank all the chapter authors for their valuable contributions. I am also grateful to my two co-editors, both of whom are experts on sharks and rays. Finally, I wish to acknowledge the staff at IntechOpen for their help throughout the editorial process.

#### **Dr. Mohamed Nejmeddine Bradai and Samira Enajjar**

National Institute of Science and Technology of the Sea, Marine Biodiversity Laboratory, Carthage University, Carthage, Tunisia

#### **Bechir Saidi**

Section 1

Ecology and Life History

Faculty of Sciences and Techniques of Sidi Bouzid, Kairouan University, Kairouan, Tunis

## Section 1
