Sílvia Vilà

Fish Health and Fisheries, Implications for Stock Assessment and Management: The Mediterranean Example

Although fish health may influence key population-level processes, particularly those dealing with natural mortality, reproduction, and growth, which, in turn, affect stock productivity, little emphasis has been placed on the links between fish health and the management of marine fisheries. This article addresses this gap and illustrates how knowledge of fish health could provide insight for marine fisheries biologists, stock assessment modelers, and managers. The study proposes ways in which the consideration of condition indicators (energy reserves) and parasitism improves stock assessment and fisheries management, especially in situations of data shortage when standard methods cannot be applied, as is the case in many Mediterranean fish stocks. This article focuses on seven case studies of different fish species from the Mediterranean and Black Seas. Overall, and although the relationship between fish health and productivity cannot always be found or quantified, the article emphasizes the importance of the physical health of exploited stocks, particularly during critical life periods of the fish (e.g., prior to spawning, migration, or in the early life stages), as an essential element of sustainable and profitable fisheries. On the basis of these results, stock assessment and fisheries management implications are discussed.

Female reproductive biology of the bluemouth Helicolenus dactylopterus dactylopterus: spawning and fecundity

The bluemouth Helicolenus dactylopterus dactylopterus is a zygoparous species that spawns multiple batches of embryos enclosed within a gelatinous matrix. Oocyte development is asynchronous, and the recruitment of secondary growth oocytes occurs continuously during the developing phase, but stops before the start of the first spawning (i.e. fecundity is determinate). The number of developing oocytes can be estimated as a function of the total length of the fish, its ovary mass and its gonado-somatic index. Only at the onset of spawning, when potential fecundity is determined, does condition also have a significant effect. The low levels of atresia detected during most of the spawning season show that this mechanism does not substantially affect the process. There is variability both in the spawning interval (with a mean of 2 days) and in the number of embryos comprising every single batch (up to 37,000). Expected effect of fisheries on the reproductive traits of this deep-sea species is also discussed.

Links between parasitism, energy reserves and fecundity of European anchovy, Engraulis encrasicolus, in the northwestern Mediterranean Sea

This study assesses, for the first time, the interrelationships between size, fecundity, energy reserves and parasitism in female European anchovy, in order to analyse the potential implications for the health of the northwestern Mediterranean anchovy stock arising from the current shortage of large individuals.

The gelatinous matrix of the teleost Helicolenus dactylopterus dactylopterus (Delaroche, 1809) in the context of its reproductive strategy

Abstract The bluemouth, Helicolenus dactylopterus dactylopterus (Pisces: Sebastidae), is a zygoparous species with internal fertilization that stores the spermatozoa in crypts within the female ovaries. It spawns gelatinous egg masses that were investigated in this study. Histological analysis confirmed that the ovarian wall and peduncular epithelia play an important role in the production of this gelatinous matrix that contained both oocytes and embryos. Cleavage and blastulae were the most frequent embryonic development stages observed and the tail bud was the latest stage reached. The chemical composition of the matrix was also investigated, revealing that water and proteins are the major components of this substance. This is the first study exclusively dedicated to the investigation of the composition, function and importance of the gelatinous matrix of H. d. dactylopterus in the context of its reproductive strategy.

Synthetic Cyclolipopeptides Selective against Microbial, Plant and Animal Cell Targets by Incorporation of D-Amino Acids or Histidine

Cyclolipopeptides derived from the antimicrobial peptide c(Lys-Lys-Leu-Lys-Lys-Phe-Lys-Lys-Leu-Gln) (BPC194) were prepared on solid-phase and screened against four plant pathogens. The incorporation at Lys5 of fatty acids of 4 to 9 carbon atoms led to active cyclolipopeptides. The influence on the antimicrobial activity of the Lys residue that is derivatized was also evaluated. In general, acylation of Lys1, Lys2 or Lys5 rendered the sequences with the highest activity. Incorporation of a D-amino acid maintained the antimicrobial activity while significantly reduced the hemolysis. Replacement of Phe with a His also yielded cyclolipopeptides with low hemolytic activity. Derivatives exhibiting low phytotoxicity in tobacco leaves were also found. Interestingly, sequences with or without significant activity against phytopathogenic bacteria and fungi, but with differential hemolysis and phytotoxicity were identified. Therefore, this study represents an approach to the development of bioactive peptides with selective activity against microbial, plant and animal cell targets. These selective cyclolipopeptides are candidates useful not only to combat plant pathogens but also to be applied in other fields.

Health and reproduction of red mullet, Mullus barbatus, in the western Mediterranean Sea

The reproductive and general health of exploited fish stocks is an essential element of sustainable and profitable fisheries. The main purpose of this study was to assess the relationships between reproduction and two important parameters of fish health (parasitism and energy reserves) in female specimens of red mullet, Mullus barbatus, from the western Mediterranean Sea. We present new data for this species on (i) the prevalence and intensity of infection by metazoan parasites; (ii) the total lipid content in muscle and gonads as a measure of condition and (iii) fecundity and egg quality as a measure of their reproductive capacity. The results show that M. barbatus is a batch spawner with an income breeding strategy, an asynchronous development of oocytes and indeterminate fecundity. The results also indicate that the three most abundant and prevalent parasites significantly affect the condition and reproduction of M. barbatus. Specifically, the digenean, Opecoeloides furcatus, causes a reduction in the female’s energy reserves, while the nematodes, Hysterothylacium fabri and H. aduncum, produce a rise in egg production but impair egg quality. These implications of the relationships between parasitism, fish health and fish reproduction should be taken into consideration in the assessment and management of exploited species.

A convenient solid-phase strategy for the synthesis of antimicrobial cyclic lipopeptides

A concise solid-phase synthesis of cyclic lipopeptides derived from the antimicrobial peptide c(Lys-Lys-Leu-Lys-Lys-Phe-Lys-Lys-Leu-Gln) (BPC194) was accomplished. Three different synthetic routes were explored. Best results were obtained using a protocol that includes as key steps: (i) synthesis of the cyclic peptidyl resin incorporating the Lys residue to be acylated protected at the N(ε)-amino group with an ivDde group, (ii) selective removal of the ivDde group, and (iii) acylation. These compounds were screened for their in vitro growth inhibition of bacterial and fungal phytopathogens and for their cytotoxic effects on eukaryotic cells. A sequence with high antimicrobial activity and low hemolysis was identified, constituting a good candidate for the design of new antimicrobial agents.

Design, synthesis and biological evaluation of cyclic peptidotriazoles derived from BPC194 as novel agents for plant protection

The search for novel antimicrobial agents to be used for plant protection has prompted us to design analogues incorporating non‐natural amino acids. Herein, we designed and synthesized cyclic peptidotriazoles derived from the lead antimicrobial cyclic peptide c(Lys‐Lys‐Leu3‐Lys‐Lys5‐Phe‐Lys‐Lys‐Leu‐Gln) (BPC194). In particular, Leu3 and Lys5 were replaced by a triazolyl alanine, a triazolyl norleucine or a triazolyl lysine. These peptides were screened for their antibacterial activity against Xanthomonas axonopodis pv. vesicatoria, Erwinia amylovora, and Pseudomonas syringae pv. syringae, for their hemolysis and for their phytotoxicity. Results showed that the type of triazolyl amino acid and the substituent present at the triazole influenced the antibacterial and hemolytic activities. Moreover, the position of this residue was also crucial for the hemolysis. The lead compounds BPC548 and BPC550 exhibited high antibacterial activity (MIC of 3.1 to 25 μM), low hemolysis (19 and 26% at 375 μM, respectively) and low phytotoxicity. Therefore, these analogues could be used as new leads for the development of effective agents to control pathogenic bacteria responsible for plant diseases of economic importance.