ANOTHER PECULIAR SITUATION FOR YOY OF BLUEFIN TUNA (THUNNUS THYNNUS) IN THE MEDITERRANEAN SEA IN 2016

The possible effects of the hottest temperatures recorded in 2016 (the hottest so far) on the bluefin tuna reproductive biology have been discussed by the SCRS in the past, but the situation in 2016 was very different. After collecting some detailed samples and data about the presence of YOY in various parts of the Mediterranean Sea, an unusual situation can be observed, showing different size-at-time by area in late summer-fall 2016, possibly mirroring early, late, fractioned and continued spawnings and different growth rates. These fish might result in future problems for age readings and ALK at least for the juveniles of bluefin tunas born in 2016. This paper provides the growth curves for the many cohorts of bluefin tuna YOY which have been detected and that were born in 2016

Report of the ICCAT GBYP international workshop on Atlantic bluefin tuna growth

In the last Atlantic bluefin tuna assessment, an age-length database coming from direct ageing was presented for the first time. It was observed that otolith age estimates for fish younger than 8 years old had a smaller size at age compared to spine (first dorsal fin radius) age estimates. This difference, although small, was enough to misallocate the year class. This misallocation was solved when introducing a vector of bias corrected aged otoliths based on paired otolithspine samples. We have identified two possible causes for over-estimating age in the otolith agelength data: the current age adjustment criterion (to convert the bands counting into ages) and a reading bias in age estimations from some laboratories. Otolith preparation and reading protocols have been reviewed. The edge type and marginal increment analysis showed that the formation of opaque zones would seem likely to occur primarily between December through to June, contrary to what was thought until now, for which a new criterion for age adjustment has been proposed

MEDLEM database, a data collection on large Elasmobranchs in the Mediterranean and Black seas

The Mediterranean Large Elasmobranchs Monitoring (MEDLEM) database contains more than 3,000 records (with more than 4,000 individuals) of large elasmobranch species from 21 different countries around the Mediterranean and Black seas, observed from 1666 to 2017. The principal species included in the archive are the devil ray (1,868 individuals), the basking shark (935 individuals), the blue shark (622 individuals), and the great white shark (342 individuals). In the last decades, other species such as the thresher shark (187 individuals), the shortfin mako (180 individuals), and the spiny butterfly ray (138) were reported with increasing frequency. This was possibly due to increased public awareness on the conservation status of sharks, and the consequent development of new monitoring programs. MEDLEM does not have homogeneous reporting coverage throughout the Mediterranean and Black seas and it should be considered as a database of observed species presence. Scientific monitoring efforts in the south-eastern Mediterranean and Black seas are generally lower than in the northern sectors and the absence of some species in our database does not imply their actual absence in these regions. However,the available data allowed us to analyse the frequency and spatial distribution of records, the size frequencies for a few selected species, the overall area coverage, and which species are involved as bycatch by different fishing gears.S

Calibration of the fish ageing services readings carried out in GBYP Phase 7, to estimate age of bluefin tuna from the eastern Atlantic stock

The Fish Ageing Services laboratory (FAS) was contracted by ICCAT GBYP in Phase 7 to provide age estimates from 2000 Atlantic bluefin tuna otolith samples. With the objective of ensuring that age readings provided by FAS follow the ICCAT reviewed reading protocol, a sub-sample calibration exercise was carried out. The findings show that band counts are similar between FAS and the group of laboratories involved in direct ageing. This is reflected by an acceptable precision between both readings. However, there is a one-year bias in the count of bands in older specimens, starting from 10-13 years of age, with a lower count by FAS compared to the rest of the laboratories. This bias seems to be due to the fact that FAS counts the bands in a different area of the otolith ventral arm than other laboratories. This counting discrepancy, although small, is significant and it would be necessary for FAS to reread the samples of specimens older than 10 years using the area close to the sulcus margin of the ventral arm

Evaluation of Atlantic bluefin tuna otolith ageing protocols

An otolith ageing bias for juvenile Atlantic bluefin tuna was detected at the 2017 population assessment. Consequently, revised reading criteria were proposed to reduce this ageing bias. To evaluate standardized and revised reading criteria, age estimates were compared to reading and radiocarbon age estimates. Age estimates showed a lack of bias and adequate level of precision for most readers, indicating that reading criteria are adequate. No bias was detected in the ageing of juveniles, contrary to the 2017 assessment findings. This may be due to the fact that one-year biases may not be noticeable given the wide age range and small sample size used in this study. Some readers showed lower age estimates for older individuals (20+) as compared to radiocarbon age estimates. Furthermore, age estimates were consistently higher than the Ailloud et al. (2017) growth curve for samples aged over 20 years, likely due to the lower mean asymptotic length of the growth curve using the Richards fitting. In terms of methodology, a potential section effect on identification of false annulus and edge type was noted

Report of the 2019 ICCAT workshop on swordfish biology studies for growth, reproduction and genetics

This report describes the June, 2019 ICCAT workshop on swordfish biology studies for growth, reproduction and genetics, hosted by the Instituto Português do Mar e da Atmosfera, Olhão, Portugal . The major objectives of the workshop were to 1) refine sampling and biological data collection protocols, 2) develop protocols and start the sample processing and analysis, and 3) plan for the project future steps. The biological sampling program was established by ICCAT’s Swordfish Species Group in 2018, aiming to improve knowledge of the stock distribution, age and gender of the catch, growth rate, age at maturation, maturation rate, spawning season and location and diet. This work will contribute to the next major advance in the assessment of swordfish status, by permitting the development of more spatially and biologically realistic population models used in both Atlantic and Mediterranean populations assessments and within the ICCAT Management Strategy Evaluation (MSE) for North Atlantic swordfish

Cerebral toxoplasmosis in striped dolphins (Stenella coeruleoalba) stranded along the Ligurian Sea coast of Italy.

This article reports the results of necropsy, parasitologic, microbiologic, histopathologic, immunohistochemical, indirectimmunofluorescence, biomolecular, and serologic investigations on 8 striped dolphins (Stenella coeruleoalba) found strandedfrom August to December 2007 on the Ligurian Sea coast of Italy. Severe, nonsuppurative meningoencephalitis was found in 4 animals, as characterized by prominent perivascular mononuclear cell cuffing and macrophage accumulations in neuropil.These lesions were associated with mild lymphocytic–plasmacytic infiltration of choroid plexuses in 1 dolphin. Toxoplasmagondii cysts and zoites, confirmed by immunohistochemical labeling, were scattered throughout the brain parenchyma of 2 ofthe 4 dolphins. No viral inclusions were seen in the brain of any animal. Other findings included severe bronchointerstitialpneumonia and pulmonary atelectasis, consolidation, and emphysema. Parasites were identified in a variety of organs, including lung (Halocerchus lagenorhynchi). Microbiologic and serologic examinations for Brucella spp were negative on all 8 dolphins. The 4 animals with meningoencephalitis had serum antibodies against T gondii (titers ranging from 1:80 to 1:320) but not againstmorbillivirus. In contrast, the other 4 dolphins were seropositive for morbillivirus (with titers ranging from 1:10 to 1:40) butseronegative for T gondii. No morbillivirus antigen or nucleic acid was detected in the tissues of any dolphin. It is concluded that the severe lung and brain lesions were the cause of death and that T gondii was the likely etiologic agent of the cerebral lesions. Morbillivirus infection was not considered to have contributed to death of these animals.[...