Section 44ad optional or mandatory

Pls let me know whether Section 44AD ( Presumtive Income) is Optional or Mandatory??

My client having turnover of 95,00,000/- & profit is Rs.4,75,000/- for FY 2013-14.It is Proprietorship fishing business.So he has to compulsarily file his return u/s 44AD or he can file Income Tax return as normally considering all deduction applicable to business?? & if section 44AD gets applicable then is he liable for Tax Audit because his profit is less then 8% of tunover. Pls give suggession as soon as possible.pls also let me know if any special provision applicable for fishing business.