The Strange Case of Tough White Seabream (Diplodus sargus, Teleostei: Sparidae): A First Approach to the Extent of the Phenomenon in the Mediterranean

Abstract

The Strange Case of Tough White Seabream although we are aware other human factors might also influence the phenomenon. To conclude, the present study gives an overview of the importance of the white seabream anomaly in the Mediterranean and encourages further research to disentangle the exact mechanisms behind this phenomenon.

Trophic, Chemo-Ecological and Sex-Specific Insights on the Relation Between Diplodus sargus (Linnaeus, 1758) and the Invasive Caulerpa cylindracea (Sonder, 1845)

“…According to professional and recreational fishermen, the ATS anomaly is not exclusive of D. sargus but also affects congeners D. puntazzo (Cetti, 1777), D. cervinus (Lowe, 1838), and D. vulgaris (Geoffrey Saint-Hilaire, 1817) as well as other Sparidae species (Casadevall et al, 2020). In our case, 30% of tested specimens displayed the ATS condition (Figure 2).…”

“…Liver and muscle data are plotted on the left and right y-axis, respectively, as mean ± SEM. ATS anomaly only occurs in specimens longer than 15-20 cm (Casadevall et al, 2020), a size that, according to length-weight relationships modeled from Mediterranean catches (Verdiell-Cubedo et al, 2006), corresponds to a BW of 189 g. Regardless of body size, stomach samples of the entire dataset were analyzed in their content to attest for ontogenetic diet shifts.…”

“…Taking into consideration the complex results we presented, it is not easy to detect a general trend or provide an unambiguous explanation for the occurrence of the ATS anomaly. Through a correlative study, Casadevall et al (2020) recently suggested copper in the form of antifouling paints and aquaculturerelated copper sulfate rather than C. cylindracea ingestion as the causative agent of the ATS anomaly. It is difficult to discriminate between the effects of caulerpin and copper because the latter does not bioaccumulate, as evidenced by the lack of any correlation between Cu concentration and fish length (Merciai et al, 2018).…”

“…However, Mediterranean fishermen had witnessed a peculiar condition of the white seabream for over three decades, consisting in the hardening of the meat and the consequent decrease in edibility following the cooking of apparently healthy adult specimens. This is known as the Abnormally Tough Specimen (ATS) phenomenon, and the underlying causes were hypothesized to be pollution (organic and chemical) and a change in feeding habits (Casadevall et al, 2020). In addition to grazing on the algae, the white seabream accumulates the red pigment caulerpin in the liver, red and white muscle, and skin tissues through the diet.…”

Pre-spawning fat and trace metals in Diplodus sargus (Pisces, Sparidae) and possible relationship with the abnormally tough syndrome (ATS)

“…This species is affected by a strange phenomenon observed mainly in the Mediterranean and occasionally reported in the European Atlantic and Macaronesia (Casadevall et al 2020). This phenomenon, called "abnormally tough specimens" syndrome (ATS) (Casadevall et al op.…”