Mitigating bycatch in Mediterranean trammel net fisheries using species-specific gear modifications.

Small-scale fisheries (SSF) use static gear which are thought to interact with marine ecosystems more benignly than towed gear. Despite this, trammel nets, one of the most extensively used type of fishing gear in the Mediterranean SSF, generate large amounts of discards, which can account for 25% or more of the captured biomass. Discarded organisms may include endangered or threatened species such as elasmobranchs, as well as non-commercial invertebrates that damage fishing gear or cause disentanglement delays.

Oogonial proliferation and early oocyte dynamics during the reproductive cycle of two Clupeiform fish species.

Although oogonial proliferation continues in mature females in most teleosts, its dynamics and the transformation of oogonia to early meiotic oocytes during the reproductive cycle have received little attention. In the present study, early oogenesis was examined throughout the reproductive cycle in two Clupeiform fishes, the Mediterranean sardine, Sardina pilchardus, and the European anchovy, Engraulis encrasicolus. Observations using confocal laser scanning microscopy (CLSM) provided extensive information on markers of oogonial proliferation (mitotic divisions, oogonia nests) and meiotic prophase I divisions of oocyte nests (leptotene, zygotene, pachytene, diplotene) in ovaries of different reproductive phases.

Tracking oocyte development and the timing of skipped spawning for north-east Arctic haddock (Melanogrammus aeglefinus).

The present study tracked oocyte development over 9 months and noted incidences of 'skipping', i.e., adults terminating their upcoming reproductive cycle, in field-caught north-east Arctic (NEA) haddock (Melanogrammus aeglefinus), currently the largest stock of this species.

Balbiani body formation and cytoplasmic zonation during early oocyte development in two Clupeiform fishes.

The Balbiani body (Bb) was examined in primary growth phase oocytes for the first time in two clupeoid fish species, the Mediterranean sardine, Sardina pilchardus, and the European anchovy, Engraulis encrasicolus, which belong to different families, Clupeidae and Engraulidae, respectively. Cytoplasmic morphological changes of early secondary growth oocytes were also investigated using confocal laser scanning microscopy, light and transmission electron microscopy. The ultrastructural observations showed that the two species develop a distinct spherical Bb.

Ultrastructural changes in mitochondria during oogenesis in two phylogenetically close fish species.

The ultrastructure of oocyte mitochondria and their contribution to the endogenous autosynthesis of the yolk was investigated in two clupeoid species, the Mediterranean sardine, Sardina pilchardus, and the European anchovy, Engraulis encrasicolus. The structure and abundance of mitochondria differ in secondary growth oocytes of the two species, whereas they are similar in chromatin nucleolus and primary growth oocytes. Sardine oocytes show a higher percentage of mitochondria in the cytoplasm as they develop.

Using clustering algorithms for identification of fish oocyte cohorts based on the characteristics of cytoplasmic structures.

In batch spawning fish, secondary growth oocytes (SGO) are recruited and spawned in successive cohorts, and multiple cohorts co-occur in spawning-capable females. So far, histological features such as the prevalence of cortical alveoli or yolk granules are conservatively used to distinguish oocytes in different developmental stages which do not necessarily correspond to different cohorts. In this way, valuable information about spawning dynamics remains unseen and consequently misleading conclusions might be drawn, especially for species with high spawning rates and increased overlapping among oocyte cohorts.

Development of a new 'ultrametric' method for assessing spawning progression in female teleost serial spawners.

The collection and presentation of accurate reproductive data from wild fish has historically been somewhat problematic, especially for serially spawning species. Therefore, the aim of the current study was to develop a novel method of assessing female spawning status that is robust to variation in oocyte dynamics between specimens. Atlantic cod (Barents Sea stock) were used to develop the new 'ultrametric' method, that is based on the progressive depletion of the vitellogenic oocyte pool relative to the rather constant previtellogenic oocyte (PVO) pool.

Zinc Uptake, Photosynthetic Efficiency and Oxidative Stress in the Seagrass Exposed to ZnO Nanoparticles.

We characterized zinc oxide nanoparticles (ZnO NPs) by dynamic light scattering (DLS) measurements, and transmission electron microscopy (TEM), while we evaluated photosystem II (PSII) responses, Zn uptake kinetics, and hydrogen peroxide (HO) accumulation, in exposed to 5 mg L and 10 mg L ZnO NPs for 4 h, 12 h, 24 h, 48 h and 72 h. Four h after exposure to 10 mg L ZnO NPs, we noticed a disturbance of PSII functioning that became more severe after 12 h. However, after a 24 h exposure to 10 mg L ZnO NPs, we observed a hormetic response, with both time and dose as the basal stress levels needed for induction of the adaptive response.