L'anisakiosi és una malaltia provocada per un cuc paràsit anomenat Anisakis. Quasi tot el peix que trobem als mercats pot estar parasitat per aquest cuc. Quan el peix és pescat i es mor, aquests cucs s'enquisten a la seva carn on hi poden sobreviure durant molt de temps. Quan nosaltres consumim peix amb anisakis vius, aquests surten del seu quist i s'adhereixen al nostre estómac o budell. Això pot provocar dolors abdominals, vòmits i diarrees. Per evitar l'anisakiosi cal eviscerar i netejar el peix el més aviat possible. A l'hora de cuinar-lo, ens hem d'assegurar que tot el tall rebi una temperatura de, com a mínim, 60°C durant almenys 10 minuts. Si volem preparar plats de peix cru o poc cuinat, hem de congelar-lo abans a una temperatura de -20°C durant 24 hores.
El mercuri és un metall pesant que a elevades concentracions és tòxic per a l'home. Aquest compost es pot trobar de manera natural al medi ambient, però determinades activitats industrials han fet que les emissions de mercuri a l'atmosfera augmentin fins a nivells crítics per a l'ésser humà. El mercuri, un cop a l'aire, precipita i cau als rius, mars i oceans on és absorbit per les algues. Aquestes són ingerides pels petits peixos herbívors i aquests, al seu torn, pels grans peixos carnívors. D'aquesta manera, la concentració de mercuri va augmentant a cada esglaó de la cadena alimentaria. Quan l'home consumeix peixos que són grans depredadors, corre el risc d'incorporar al seu organisme importants quantitats de mercuri. Això pot afectar la seva salut, sobretot, la dels nens ja que el mercuri té efectes nocius sobre el desenvolupament neurològic. Així doncs, les dones embarassades i els nens haurien d'eliminar o reduir el consum de peixos que siguin grans depredadors com la tonyina i l'emperador i menjar, en el seu lloc, altres espècies que es trobin al principi de la xarxa alimentària com la sardina i l'anxova.
This workshop, organized by the Research Group “Biologia Animal-Ictiologia" and financed by the Spanish Ministry of Science and Innovation (Acción complementaria CTM2009-07342-E), was held at the University of Girona on the 7thof July 2010.
This workshop aimed at opening up new directions in marine fish health research with a potential impact on the assessment and management of exploited resources. It brought together eight marine scientists from four different countries (Spain, France, Italy and Ukraine) with different expertise in the field of fish health (parasites, condition indices and reproduction) to discuss on recent advances in that field, the gaps in knowledge, the future research needs and the use of fish health as indicator of population conditions from an ecological–fishery perspective. Additionally, the workshop allowed participants to outline future research perspectives that could allow a joint interdisciplinary effort for the investigation of fish health.
Table 1. List of participating experts
|Georgiy Shulman||Institute of Biology of the Southern Seas, Ukraine||Fish condition|
|Simonetta Mattiucci||University of Rome, Italy||Parasitology|
|Betty Faliex||University of Perpignan, France||Parasitology|
|Pierre Sasal||CNRS, Moorea, France||Parasitology|
|Toni Raga||University of Valencia, Spain||Parasitology|
|Josep Lloret||University of Girona, Spain||Fish condition|
|Margarida Casadevall||University of Girona, Spain||Fish reproduction|
|Marta Muñoz||University of Girona, Spain||Fish reproduction|
Topic 1: State of the art
Dissection of a Coryphaena hippurus
The participants discussed the biggest unknowns in understanding health of marine exploited species, the impact of parasitism on fish condition, the influence of fish condition on reproduction of fishes and the relationships between host genetic diversity and parasitic load. In particular, the participants:
Topic 2: Methodological aspects
Different approaches used to evaluate health of fishes were presented. The topic discussed the pros and cons of the different methods and indicators to estimate fish parasitism, condition and reproductive potential, and looked for the new methods that are being developed to evaluate these variables (e.g. molecular techniques). The topic also discussed on the existing long-term databases on fish condition and parasitism regarding the possibility of developing standardized inventories to make comparisons possible. In particular, the discussion considered the following aspects:
Topic 3: Application of health indicators in the management of marine resources
Scorpionfish caught with a trammel net
This topic discussed on the possible applications of fish health indicators into the assessment and management of fish populations, and how fish health variables could be better integrated in fish population models. A major consideration of the topic was how fish condition indices and fish parasitism can be used as population and ecosystem status indicators. The discussion considered the following aspects:
Topic 4: Future research
During this session, the main research priorities and future available funding opportunities were discussed to keep the activities of the group growing. The participants settled specific ideas for future research collaboration in the European area. The discussion considered the following aspects:
Sea breams (K. Dimitriadis)
1. Fish parasites: the participants summarized the interest of these studies in relation to fisheries management in the following aspects.
a. The utility of fish parasites to identify fish stocks. Parasites can thus be used as biological tags in fish stock characterization.
b. The impact of fish parasites on fish stocks, whether it is through the effect on energy reserves, reproduction or natural mortality (M).
i. Regarding energy reserves, although theoretically the effect of parasites on fish energy reserves should be negative, in practice the relationship can be negative (when fish are intermediate hosts: transmission of parasites) or positive (when fish are final hosts: food acquisition). Sometimes even there is not a significant relationship between both variables because the indicators of energy reserves are not good enough (e.g. use of simple morphometric indices). In this sense, the impact of parasites on lipids of Engraulis encrasicolus was discussed.
ii. Regarding reproduction, participants discussed the impact of parasites on sex reversal, egg loss, fecundity and gonadosomatic index (GSI). In this regard, the impact of parasites on reproduction of Anguilla anguilla was discussed.
iii. Regarding natural mortality (M,= the negative impact is being tested in Mola mola. The participants also discussed on the fact that what is bad for the individual (e.g. a parasite that kills an individual fish) is not necessarily bad for the population (after this individual fish is killed, the rest may have more food to feed on)
c. The utility of fish parasites as biological indicators of marine trophic webs and of overfishing (particularly overfishing of definitive hosts).
d. Study of host-parasite co-phylogenetic aspects (Xiphias gladius was shown as example)
e. Although parasites are always thought (by definition) to have negative effects on species, the participants pointed out that they can also act as beneficial organisms for the ecosystem and its diversity can be indicator of good ecosystem health.
f. The possible increases in parasitic loads in certain areas (e.g. Catalonia) should be studied in deep, as well as the possible causes (sea warming, increase of pollution or in the abundance of marine mammals) and consequences on fish stocks. Despite the possible economic and ecological implications, these ecological aspects of fish parasitism have been seldom studied.
1. Fish energy reserves (fish condition indices): the participants summarized the interest of these studies in relation to fisheries management in 3 aspects:
a. Energy reserves, particularly lipids, are an important attribute of fishes because they have a large influence on growth, reproduction and survival. Low energy reserves may lower the chances of survival, leading to an increase of natural mortality. Starvation due to exhaustion of energy reserves, particularly during the non-feeding and reproductive periods, weakens fishes and renders them more susceptible to predation and fishery, diseases and to a variety of environmental stressors. Inadequate reserves have been implicated in the reduced reproductive potential of several fish species through reduced fecundity and quality of eggs and larvae or delayed maturation (reviewed by Lambert et al. 2003). A reduction in fish energy reserves does not only affect the own population success but may impact as well on the reproductive output of top predators.
b. From all indicators of energy reserves, total lipids is the most widely used because it is easier and less expensive to determine than other indicators such as omega-3 fatty acids or glycogen (which are, however, better indicators than total lipids, particularly in some fish groups such as gadoids, where glycogen is as very import source of energy, or pelagic fishes, where omega-3 fatty acids are very important). Furthermore, total lipids are usually correlated negatively with water content (once this relationship has been established, the total lipids can be determined easily from the water content). The use of physiological indices such as liver index can be suitable for those species storing energy in the liver. The use of simple morphometric indices such as Fulton’s K and Le Cren relative condition factor Kn should be avoided and only used as a first proxy of fish energy reserves in the long term when great numbers of length and weight data exists.
c. The best time for collecting condition data will depend on the species but in a first sight should consider the maximum values of energy reserves, which usually will be just before reproduction and/or end of the feeding period (if it exists, e.g. anchovy and sardine). It should be also evaluated during spawning.
5. Fish reproductive potential: The participants summarized the interest of these studies in relation to fisheries management in 2 aspects:
a) The reproductive potential of fishes is increasingly being used for fisheries management purposes. Different networks and groups of fisheries biologists working on reproductive potential of fishes such as the Northwest Atlantic Fisheries Organization (NAFO) working group on reproductive potential of fishes and FRESH (Fish Reproduction and Fisheries; cost action; www.fresh-cost.org) have been constructed in the last few years.
b) It is a key aspect in determining the success of the population. Several indicators have been proposed, from simple ones (gonadosomatic index) to more complex ones (atresia, fecundity, sex reversal). These indices should be considered on a species basis, and taking into account their dependence on parental health (parasites and energy reserves)
6. Future collaborations. The participants agreed to follow the cooperative work in the establishment of a network of fishery scientists working on fish health for fisheries management purposes in the Mediterranean and the Black Seas. The network will focus on parasites, energy reserves (condition indices) and reproduction of exploited marine fishes.Although the embryo of this network is made by the participants in the workshop held in Girona, the network should be enlarged with the incorporation of new scientists working in these topics from a fishery perspective. In order to make this network larger and well settled, the participants of the workshop agreed to search for further funding such as European Science Foundation (ESF) exploratory workshops or Marie Curie Initial Training Networks.
For more information please contact Josep Lloret