The boat set out in early December with as many as 124 people on board, thought to be headed for the Canary Island, but it ran aground in bad weather.
Fishermen rescued 24 people from the boat on Saturday off the northern coast of Senegal.
At least half of the almost 30,000 illegal arrivals in Spain’s Canary Islands in 2006 have been Senegalese.
Hundreds of people have already died at sea this year as they try to make the perilous crossing from Senegal or Mauritania to the Canaries in overcrowded fishing boats.
Medical officials say the 24 survivors under observation in a hospital in St-Louis in northern Senegal, are dehydrated and malnourished after approximately two weeks at sea.
Awa Sow, whose son Souleymane was rescued, was outside the hospital where other relatives have gathered.
“If he took all these risks, it’s because he saw the situation his family was in,” she told Associated Press news agency.
Many West African job seekers hope to use the Canaries as a jumping off point to illegally enter mainland Europe
The BBC’s Tidiane Sy in the capital, Dakar, says this is the third boat in a week to be confronted by problems in the high seas leading to loss of lives.
It happened only a few days after the visit to Dakar by Spanish Prime Minister Jose Luis Rodriguez Zapatero, whose country agreed with Senegal to reinforce sea patrols.
Joint patrols try to prevent illegal immigrants reaching Europe by this avenue.
These stricter controls, combined with the bad weather at this time of the year, are believed to be the main causes for the many wrecked boats, our correspondent says.
Nevertheless none of these factors is deterring the determination of those attempting these deadly trips.
The Senegalese government is giving as little publicity as it can to the tragedy and the private media have very little access to the rescued passengers, our reporter says.
With elections due in about two months, the government is facing heavy criticism for failing to deliver on its electoral promises to create job opportunities, our reporter says.
Spain and Senegal have agreed a series of measures to curb illegal migration to the Canary Islands and repatriate some of the migrants.
The European Union set up a rapid reaction force of border guards, called Frontex, to try to tackle the influx of migrants.