Our knowledge of the many different
types of reproductive strategies of sharks is still limited. This
variety is precisely why it is difficult to make generalisations on
their reproductive methods, although this is exactly what makes
sharks so successful.
Types of reproduction
Most sharks bear live young
(viviparity) and the others lay eggs. Several shark species mate the
entire year, others prefer certain seasons and regions. The females
of some shark species bear young each year whilst others stop
reproducing at irregular intervals which can last several years.
Viviparity
Oviparity
Ovoviviparity
Mating
Few people have witnessed the mating activity of sharks. In smaller, more
flexible species the male coils around the female. Whereas, males of
larger, more rigid species will orient themselves parallel and
head-to-head with females.
During mating, males of many species bite females on the
pectoral fins or the middle of the back to hold onto them. Females
often bear scars or marks. As
a result, some female sharks, such as the blue shark, have skin on
the back and flanks more than twice as thick as the skin of the
male.
Sexual Appendages
Claspers are modified inner edges of the pelvic
fins of male sharks and rays. During copulation, the erectile
claspers are bent forward. The male inserts one clasper at a time
into the female. In some species, claspers contain cartilaginous
hooks and spurs that "clasp" into the walls of the female oviduct,
anchoring the clasper. Muscles force seminal fluid down a groove in
the clasper and into the female oviduct.