The remains of 204 migrants were retrieved of the 1,020 who disappeared while attempting the crossing between January 1st, 2018 and April 30th, 2019, migrant rights NGO Caminando Fronteras or “Walking Borders”in English, said in a report.
There are certainly other” victims, Caminando Fronteras head Helena Maleno told a news conference.
“But we are certain of these cases because our job is to investigate with the families, to put a name to each (victim) and document how these shipwrecks happen. Families are being denied the right to mourn,” she added.
The group's figures are close to those of the International Organization for Migration (IOM) which found that 952 migrants died or were missing while trying to reach Spain from North Africa since the start of 2018.
Following crackdowns on immigration by Italy and other countries, Spain last year became the preferred route to Europe for migrants although those numbers started falling dramatically at the start of this year.
Many have crossed the 15-kilometre (9-mile) Strait of Gibraltar from Morocco, often in small, overcrowded inflatable boats unfit for open waters.
Activists accuse European countries of leaving sea rescues to Morocco and other North African countries with fewer resources and experience, potentially putting lives in danger.
Maleno said Spain was doing “practically the same thing” as Italy's hardline Interior Minister Matteo Salvini and “withdrawing” from migrant rescues in “a more disguised way”.
Spanish Interior Minister Fernando Grande-Marlaska said last week that Spain's policy regarding the rescue of migrants has not changed.
Twelve boats carrying migrants to Spain have gone missing in the Mediterranean Sea since the start of 2018, according to Caminando Fronteras.
“These tragedies are the most distressing and hurtful because of their impact, no survivor can establish a story and the truth of the disappearances,” the group wrote in its report.