Fish-based remedies in Spanish ethnomedicine: a review from a historical perspective

Background Fish-based therapeutics is fundamentally based on a dietary use, but these vertebrates have also been employed in the treatment of infectious and parasitic diseases, during pregnancy, childbirth and postpartum and to deal with diseases of the different systems. Methods An overview of the ethnomedical and historical Spanish literature has been carried out. Automated searches in the most important national and international databases have been performed. All related works have been thorough examined. Results We examine the historical use of 54 medicinal fish species, 48 marine and six from inland waters. As useful, in Ancient times 39 species have been recorded (of which only 21 have been collected in subsequent periods), seven in the Middle Ages, 18 in Modern times and 17 in the contemporary period. Anguilla anguilla, Engraulis encrasicolus or Scyliorhinus canicula are species that have survived over time as an ingredient in Spanish folk remedies. Most remedies used in the last century and currently are empirical remedies based on the humorism theory and the principle of contraria contrariis curantur (74%), and the rest (26%) are magical type remedies that complete the popular therapeutic arsenal. Conclusions In the last century we find a progressive decrease in the number of fish species used in ethnomedicine. Only seven taxa have been documented as surviving therapeutic resources since centuries ago. The existence of a dynamic Spanish ethnomedicine has also been detected which has managed to generate new therapeutic resources in recent times. It is important to validate the remedies by ethnopharmacology and evidence-based medicine. In order to recover as much data as possible, it will be necessary to draw up an inventory of ethnoichthyological uses.


Background
Ethnozoology is an emerging field in many areas of the world and it is divided, due to its multidisciplinary character [1], into branches of knowledge such as ethnoentomology, ethnoherpetology or ethnoornithology [2][3][4].
Fishes have a long history of interaction with humans, thus "ethnoichthyology" is acquiring an important role in ethnozoological research [5][6][7]. There are some studies that discuss the role of ichthyofauna in traditional medicines, mainly in fishing communities [8][9][10][11][12], and that reveal a large number of fish species used in zootherapy, understood as the medicinal use of animals and animal-derived products to treat illnesses and health conditions [13,14].
These works on zootherapy are a very useful tool in the exploration of pharmacologically active substances [15,16]. But also there are other reasons of an anthropological kind for carrying out these ethnozoological studies. For example, they can help us in the understanding of the human behavior toward health care and the use-consumption of fish resources. As well, in many developing countries these studies have a great value in fish diversity conservation [17][18][19].
In Spain there has not been any ethnozoology development and only very few articles have been published with an ethnobiological approach, although some anthropological, folk and ethnomedicinal studies have focused on the connections between human society and animals [20][21][22][23]. This has affected the study of the interactions between humans and fish (ethnoichthyology), and the zootherapy based on these vertebrates is a field of research that has not been given due attention and must therefore be constructed from a framework of an "historical ethnozoology". Following this philosophy, this paper illustrates the use of fishes in Spanish ethnomedicine and its historical development as a therapeutic resource. It provides an inventory of the species that have been used for medicinal purposes from ancient times to the present, and analyses the medical use of fishes in the 20th century.
Thus, our main objective is to obtain an inventory of the fish species that have been used in Spain for therapeutic purposes from antiquity to the present. From this we determine which medicinal species have survived to recent times and what diseases or medical conditions they have been used for.

Procedures
The present study forms part of a project revision of the ethnozoology in Spain, for which various databases have been examined: ISI Web of Science and Anthropology Plus, JSTOR III -Arts and Sciences, TESEO, the information system of the databases of the Consejo Superior de Investigaciones Científicas (CSIC), the bibliographic website Dialnet, Google Scholar, and the catalogue of Public State Libraries (BPE). The search focused on the type of documents contained in folklore, ethnographic, history of medicine and social and medical anthropology studies. The key words used were: anthropology, history of medicine, ethnomedicine, folk medicine, folklore, zoology, ethnozoology and ethnoichthyology, and the names of the different fish groups in Spanish or English, as appropriate. The search framework also made use of a list of zoonyms contained in Spanish dictionaries [24], and a directory with the names of the most relevant authors of therapeutics throughout history.
The search results were catalogued and the information was classified into ichthyologic groups and historical periods, according to the classical periodization followed by Christoph Cellarius (1638-1707) and those recently employed by De Vos [25]. A total of 52 documents have been analyzed , of which approximately 8% belong to Ancient history, 10% to Medieval, 10% to "Modern" (6% to 15th-17th centuries and 4% to 18th-19th centuries, respectively), and 72% to "contemporary history", i.e. from beginning 20th century to present ( Table 1).
The method of identification of the fish species consisted of a discriminatory analysis of the biological, ecological and ethological information, and of the vernacular nomenclature contained in the works consulted. This was all corroborated with catalogues of names, single-access or dichotomous keys of fish [79][80][81][82], and ichthyological databases and species identification websites [83][84][85][86][87]. The assessments have been made from Spanish species, although in some cases taxa from other jurisdictional waters or maritime territories have been considered. Those valid scientific names included in the Species 2000 and ITIS Catalogue of Life: 2013 Annual Checklist [88], are considered in the list of species. The species of most historic importance have been established according to their inclusion in the remedies belonging to the 20th century and at least one previous era.
The illnesses treated with the species mentioned are classified using the chapters of the International Statistical Classification of Diseases and Related Health Problems 10 th Revision, ICD-10 (Version: 2010) [89]. Taking into account the species employed in the past century, the relative importance of each group of diseases (IC i ) in Spanish ethnomedicine has been calculated. A calculation has been made of the relationship between the number of useful species registered for each chapter (C i ) and the number obtained for the chapter with greatest species richness (C max ); i.e. IC i = C i /C max .

Data analysis
The Spanish ethnomedicine applies to medical ideas and practices with magical, religious and natural (empirical) background [43,45,49,64,71]. In this regard, we have classified all the documented remedies despite difficulties in establishing boundaries for this kind of work review method since remedies based on empirical knowledge are found as well as magical-religious therapies with both empirical and esoteric bases. In accordance with the previously mentioned, the categories for type of remedy are as follows: "magical remedies" and "empirical remedies" (i.e., natural medicine home remedies for those using fish parts for therapeutic means starting from an empirical base).
On the other hand, to evaluate the route of administration of the remedies, we consider two categories: "internal use" and "external use".
All these are categories make up the variables studied in a test of independence once the values obtained in two-by-two contingency tables were included. The Pearson's chi-squared test (χ 2 ) was used to answer the question of no association between variables. This test rejects the null hypothesis (of independence) for statistic values too big to be attributed to random chance. All of this allows us to answer the following key question: The fish-based remedies that have survived in the Spanish ethnomedicine have similar features to those remedies listed in the most relevant historical references?

On the determination of the species
There is no doubt that the identification of species that appear in historical and classical works is inherently difficult. In relation to this problem on taxonomic interpretation Josefa Cantó writes: "The difficulties are varied: scarcity and inconsistency of data-often saying incompatible things about the same species in different-passages; even Pliny makes mistakes, sometimes he misinterprets his sources and combines names and characteristics that do not correspond to the same species. It contributes to the confusion that sometimes he uses two different names, one Greek and one Latin, for the same fish. Besides data from ancient texts about size, colour, habitat, habits, etc., the etymology of the names or their possible survival in Romance languages may help. It's important to enlist the help of biologists since their knowledge of marine species allows a better guess at what may lay hidden behind a superficial description" [26].
We include some fragments of the work by Francisco Vélez de Arciniega published in 1613, entitled Historia de los animales mas recebidos en el uso de medicina: donde se trata para lo que cada uno entero ò parte del aprovecha y de la manera de su preparacion…, which has been useful to make a differential diagnosis of some species. This work is of special interest because it synthesizes descriptions of Aristotle, Dioscorides, Pliny and Galen, among other classic authors.
In the fourth book De los pescados recebidos en el uso de la Medicina, Vélez de Arciniega "De las Menas" and "Del Smarido" tells us that: "Menas are very similar to Smaridos, which (according to Pliny) change colour at different times of the year, and are white in the winter and black in the summer. They swim collectively in the sea, near the shore" [36].
The differential diagnosis leads to Spicara maena and S. smaris. The "mena" is S. maena, which presents a very variable coloration according to sex, age and season. Spicara smaris, the "smarido", unlike which has a silvery, gray back and as the text indicates swims in important shoals.
"Del Gobio" we get Crystallogobius linearis: "It is a small fish the gobio, which has a big mouth in proportion to the body: belly it has many strands close to its belly, it is glutinous: and so very easily be slips between the hands. According to Aelianus: The Gobio, Dragon and Sea Swallow, pitch poison, but it is not fatal … They lay (according to Aristotle) their eggs on the banks, against the stones and in the sands" [36].                 This description is compatible with C. linearis, which has a size of 4.7 cm in the male and 3.9 cm in the female, it has a big mouth, its first dorsal fin has two conspicuous radios in the male and external muscle segments just as suggested the text. Its range includes the Atlantic (it goes as far as Gibraltar) and the Mediterranean. It is a benthic species commonly found on shells and on sandy bottoms. In Dioscorides, some authors associate the word "gobio" to the Gobio gobio species [27], which is a freshwater fish with a small mouth and which lives in sediment covered beds. Andrés de Laguna, commenting Dioscorides, states that: "The gobio is a well known fish on all the shores of the Adriatic Sea, although it is also found in some lakes and rivers, the head of the gobio is in proportion to the body, very great: it is very tasty and easily digested, having very delicate meat and is a good nutrient, mainly those which are caught between some rocks" [90].  From the explanation in "Del Scorpion Marino" we get Scorpaena porcus: "The Scorpion grows within the Pielago, and Scorpina in more swampy places. Scorpion is red in colour and Scorpina almost black. "He" is good gentle food and "she" not so. Scorpion has a flap on the back with twelve sharp spikes, and a very large spiked head: it has short, thick teeth and very small, thin almost invisible scales" [36].
The morphological character, a large head and a dorsal fin with 12 hard spines and 10 soft rays allows the identification of S. porcus. These characteristics of the species distinguished it from Trachinus radiatus also known in Spain as "escorpión" (scorpion) or "araña" (spider), which is of a dark colour on the back and has six hard poisonous rays in the first of the two dorsal fins. It should be noted that Pliny refers to both the dragon and the scorpion when he writes "which have stings in the gills facing the tail, and thus sting like a scorpion when you pick them up" [26]. In this case the "scorpion" would be T. radiatus, in addition to the characteristics described, presents poisonous opercula spines oriented toward the tail.

Ethnomedical practices: useful species and remedy features
Many species documented in this study as useful in the therapeutic are species currently marketed and consumed in Spain (Figure 1). The most historically important fish species, with use-reports in the 20th century and in one or more past periods, and whose usage has survived over time, are: Acipenser sturio, Anguilla anguilla, Engraulis encrasicolus, Halobatrachus didactylus, Hippocampus sp., Scyliorhinus canicula and Squatina sp. (see Table 2).
Cod (Gadus morhua) is the species for which we have found a large number of use-reports (24). Although some remedies are based on the use of its jawbones, fins or gills, the importance of this species lies in the frequent use of cod liver oil to treat nutritional problems and the intake of meat of dried and salted cod to stimulate the secretion of milk and prevent seasickness. At this point, it should be noted that the salt cod was for many decades the only fish stored and consumed by the rural communities of the central part of Spanish territory ( Figure 2).
According to the results obtained from the statistical analysis performed to evaluate the features of the different remedies found, we can conclude that the route of administration of a remedy and the periodization (historical periods vs. contemporary times) are independent (χ 2 = 2.850, df = 1, p = 0.091). By contrast, there does exist an association between the type of remedy and the periodization (χ 2 = 15.751, df = 1, p < 0.0001), they are not independent.
The number of fish-based empirical remedies is significantly larger as well as the number of magical remedies in the case of the historical periods ( Figure 3). These differences are not due to random chance.

Concerning therapeutic foundations and medicinal value
Magic and superstition are poorly understood concepts in some contexts and situations. Many remedies can be labelled as superstitions or magic, but is all that is branded superstitious or magical really so? From an anthropological viewpoint magic can be defined as "a combination of beliefs and practices based on the conviction that the human being can intervene in natural determinism, albeit completing or modifying it, by means of the manipulation of certain powers, accessible through aptitudes, knowledge, or special techniques" and superstition as "a knowledge or belief considered erroneous and not accepted by whoever has the authority to distinguish between legitimate and illegitimate knowledge" [91,92].
Superstition in medicine has been evaluated by Luis Gil in his work Therapeia. La medicina popular en el mundo clásico [93] in which he interprets the curative procedures of the animal-based medicine throughout history, with some words from MacKinney [94].
"It cannot be denied that the later Greek writings in medicine contain remedies that are more primitive than those of Hippocrates' time. The same phenomenon, rise in superstitious prescriptions when a civilization ages, can be observed in other historical periods, especially in Ancient Egypt and Medieval Europe. However, this fact does not justify the conclusion that medical science gives way to superstition when a civilization ages. Thus, the writings of the later centuries contain an ever-increasing load of data, not only of science, but also of superstition, which includes that transmitted in previous eras. The Ebers Papyrus contains recipes from previous periods. The same is true of De Materia Medica, compiled by Dioscorides in the late period of the Greek civilisation" [93].
In zootherapy it can be affirmed that belief systems have been significant throughout history. Empedocles and Plato considered the importance of therapy not based on reason [95,96].
The magical theme of medicine is observed in the remedies compiled, in such a way that some are based on "transferential therapy", where the illness or pain is redirected to the animal, as happens in the case of poisonous bites or stings. We can cite, for example, species that act as antidotes when applied directly to the skin, such as Sarda sarda, Thunnus thynnus, Mullus sp. (M. barbatus barbatus, M. surmuletus), Trachinus draco, T. radiatus, Scorpaena porcus or Dasyatis pastinaca (see Table 3).
Astrology exercised an influence on ancient pharmacopoeia by relating therapeutic capacity to favourable astral constellations. In the Zodiac Man or homo signorum of Burriana (province of Castellón) we can observe that a link was established between the astrological signs and various parts of the body [97]. Thus, we find that by presenting a woman in labour with a "tembladera" (Torpedo marmorata, T. torpedo), caught when the moon is in Libra, the delivery will be made easier. The astrological systems used animal symbols to explain how different parts of the human body are related to illnesses. These human body-animal associations seem to have largely originated from sympathetic magic, whereby each animal possesses specific facilities which can justify their relation to a certain part of the body, to which their "virtue" would be transmitted. In the Old World, fish, recognised for the agility of their movements, were related to feet [98]. Accordingly Table 3 shows folk remedies for the treatment of gout and knee and foot joints pains (Anguilla anguilla, Lophius piscatorius).
Dolores Carmen Morales has carried out an analysis of fish, noting the link between this animal group and reproductive apparatus and fertility: "As for fish, the symbol of Jesus par excellence, they maintain their high reputation in Christianity due to their inheritance from other cultures. Psychic or sacred animals, fish have, however, been read in other ways: sexual interpretations because of their phallic form. Sacred Writings cite them on various occasions, possibly the most relevant reference being the miracle of the multiplying of the bread and fish. Fish are also a symbol of fertility because of the quantity of eggs produced" [99].
Thus, in Table 3 we see remedies for disorders or diseases related to the reproductive system, which follow a sympathetic magic where "like produces like", as happens with the remedies that aid childbirth, based on species such as Anguilla anguilla, Torpedo marmorata, T. torpedo, Silurus glanis or Dasyatis pastinaca; increase the production of milk with Spicara smaris and Gadus morhua; and are used as aphrodisiacs, as Anguilla anguilla and Pagellus erythinus.
We find remedies based on sympathy associated to other systems, like the application of Torpedo sp. for the treatment of diseases related to the spleen, due to its similarity in form. In the same way, otoliths or "stones from some fish" (sensitive structures to gravity and linear acceleration) are associated with the treatment of kidney stones, as in Argyrosomus regius and Merlangius merlangus (Figure 4). The red colour of Mullus barbatus Figure 2 A bit of dried and salted cod. In Spain the "bacalao" is used in the culinary preparation of numerous and diverse traditional dishes. This product is consumed raw in salads, stewed or eaten fried. barbatus or M. surmuletus means that these species can be used for the treatment of menstrual disorders, and the form of the adhesive disc of the head of Remora remora explains its use in easing the implantation of the embryo in the uterus, as suggested in vernacular names "chupón", "chupona", "ventosa" (sucker, plunger, suction pad), typical of the Cádiz and Huelva coast [100].
Hippocratic medicine was the natural philosophical foundation for therapy since antiquity up to the development of biomedicine in the 19th century. Humoralism explains the physiology of the body in terms of a balance between the four humours or fluids: black bile, yellow bile, phlegm and blood. The excess or deficiency of these humours, as a consequence of life style, would provoke diseases, disorders or conditions that would have to be corrected in order to recover health [101,102]. Juan Sorapán de Rieros, in his work Medicina española, contenida en proverbios vulgares de nuestra lengua (1616), associates one of the humours -phlegmwith fish: "And to understand this, that of the four humours, which are in our body, one of them is called phlegm, whose nature is cold, and humid like water. It forms mainly in the stomach, and more so in winter (according to the doctrine of Hippocrates) and with food stuffs that are cold and wet, sticky and difficult to cook. Part of this phlegm stays in the stomach, and part of it passes to the liver, where in time of need, it is perfected by the body's natural heat is converted into blood. There are two differences of phlegm, one that is natural, and another that is not natural. The natural one is white and tasteless. The unnatural, is sour, or is salty, or glassy. Natural phlegm and things similar in their qualities can easily turn into each other, according to the philosopher's doctrine. Fish, in nature is cold and wet, like phlegm, and can change into it. And in this sense it is true to say that, all fish is phlegm" [103].
In Hippocratic medicine treatment by opposites or antipathy, contraria contrariis curantur, is an overriding principle which is based on primitive associations between opposites [93]. Although it's risky to interpret the remedies, we can glimpse the pharmacological conceptualization of this principle to counteract the heat and dryness of many symptoms that would be caused by stomach bile, for example by infectious diseases such as rabies, mumps, malaria and tetanus, taking advantage of the phlegm provided by Hippocampus sp., Trachurus trachurus, Perca fluviatilis or Lophius piscatorius. Digestive diseases that caused dryness or black bile would also be balanced with phlegm, thus Coris julis, Spicara smaris, Sardina pilchardus or Silurus glanis were used as laxatives.
It should be noted that although the Hippocratic Corpus constantly reported apathetic and allopathic treatments, you can also find homeopathic treatments within its pages [96,102]. Therefore we can suggest a Hippocratic origin for the remedies which use phlegm against phlegm, such as the treatment of respiratory problems with Silurus glanis.
The empirical trend based on discerning the type of remedy that was useful in the treatment of a given disease appears in the Historia de la Farmacia by Quintin Chirlone and Carlos Mallaina in 1865, where it states the following: Is it not known, for example, that people with a putrid fever ask for acids and certain fish please those with leucorrhoea and that dysentery is characterized by a particular appetite for grapes? [104]. The otoliths of this fish species acquire a shape in which many people say that they see the face of the Virgin Mary, a fact that makes these mineral structures in a reputed protective amulet. In the pendant presented here we can see one of these otoliths mounted in gold. It belongs to the mother of one of the authors (JRV, Badajoz), who carries this jewel around her neck to prevent attacks of lumbago.
Thus, we can note that throughout history species have been selected and have been used in all historical periods because of their empirical effectiveness. Although looking back we can find critics of the popular empirical medicine such as Abü Muhammad 'Abd Allah b. Rusd in his work Acerca del método de la técnica artesanal en la terapéutica, in which he writes: "It is clear that when a 'doctor' treats a patient with any substance, he thus provides Nature with a beginning and an end of order, whether it be in the genre of disease or of health. But if the 'doctor' is ignorant of this natural order and proper purpose and gives Nature any random beginning -I mean treating the sick with whatsoever-he may in essence be wrong but accidentally gets it right, causing more deaths than health. It is clear that ignorance of this method is the cause (fol. 79 r.) or at least one of the causes that the wise ascribes to the origin of sensation and the sensible. But we are talking about health and about disease, because most deaths occur due to the medicine" [105].
Despite the existence of detractive positions against zootherapy there currently exists objective data which demonstrate the efficiency and potential of fish as a therapeutic resource. In this regard, we underline the synthesis by Fariña Pestano et al. [6] which refers to the narcotic and analgesic active ingredients found in Tetraodontidae fish [106] -used in Japan with patients diagnosed with neurogenic leprosy and cancer [107]-to a cardiac stimulant obtained from Eptatretus stoutii Linnaeus, 1758, antitumor agents in Dasyatis sabina (Le Sueur, 1824), analgesics in Taricha sp.; well as to the properties of omega-3 fatty acids obtained from shark liver in preventing atherosclerosis, hypertension, in wound healing and the stimulation of the immune system of alcoxiglycerol [108] collected by Costa-Neto [109].
Recently, researchers at the University of Almería have undertaken a study of 12 commonly consumed fish species in the southeast of Spain, demonstrating that the liver of these fish is an excellent source of fatty acids of the omega-3 family [110]. These long chain polyunsaturated fatty acids are currently used in the treatment of degenerative diseases of the nervous system and in mental health [111].
As already mentioned, the historical and therapeutic value of the fish fauna in Spanish ethnomedicine is expressed in the survival of medicinal resources belonging to, at least seven species throughout history: Acipenser sturio, Anguilla anguilla, Engraulis encrasicolus, Halobatrachus didactylus, Hippocampus sp., Scyliorhinus canicula and Squatina sp. In addition, there are 10 species of which we have only obtained records from the 20th century: Argyrosomus regius, Clupea harengus harengus, Cyprinus carpio, Dicologoglossa cuneata, Gadus morhua, Luciobarbus sclateri, Merluccius merluccius, Oxynotus centrina, Salmo trutta and Sardina pilchardus. This is particularly significant, for it indicates a dynamic Spanish ethnomedicine capable of generating new therapeutic resources in recent times. For these reasons, and taking into account that ethnomedicine in Spain is a medical system that has been virtually totally replaced by biomedicine, there is a need for further research in line with the methods and goals of the Spanish Inventory of Traditional Knowledge [112].
Coinciding with Quave and Pieroni [113] we think it is necessary to validate ethno-pharmaceutically those animal remedies that have stood the test of time, for it is this survival that is proof of its therapeutic potential and its possible applications in the pharmaceutical industry. During the 20th century, the most important groups of pathologies treated with fish-based remedies are: infectious and parasitic diseases, followed by those related to pregnancy, childbirth and postpartum, and diseases of the musculoskeletal system and connective tissue (see Table 4).
Significantly, those chapters of ICD-10 which are not represented are diseases of the nervous system and the ear and mastoid process, as well as congenital malformations, deformations and chromosomal abnormalities. Two out of three remedies used in the 20th century (74%) are empirical, based on the humorism and the principle of contraria contrariis curantur ("the opposite is cured with the opposite"). The rest, 26%, are magical type remedies that complete the popular therapeutic arsenal.

A cross-cultural comparison
Although less important than other groups of vertebrates, fishes are represented in ethnopharmacological studies related to traditional medicine of different geographic regions and human communities [10,[114][115][116]. This fact facilitates us to carry out a cross-cultural approach in relation to current fish-based zootherapies.
The medicinal species collected in this study are not used in remote areas of the northern hemisphere, but if they are employed species belonging to some documented genera. In India the eel (Anguilla bengalensis in this case) is used: its body mucus is applied on burned zones of the body [117], and fat is applied and massage to relieve rheumatoid-arthritis pain [118]. In the same way, at Jeju Island (Korea) the salted heads of Engraulis japonica are used to treat head lacerations [119].
Comparing with the data documented by other authors for other areas of the Mediterranean Region [113,120], firstly point out that the 17 fish species used in contemporary Spanish ethnomedicine constitute a very high number of therapeutic resources. And as to common species, the use of "bacalhau" (Gadus morhua) in Portugal is remarkable. In our neighboring country, this species is used against diseases such as anorexia, anemia and madness, in the treatment of abdominal pains and bone fractures, just like anti-fever and anti-parasitic [120].
These latter data induce us to discuss if there are species or similar (same family, for example) that also are used in the American countries were colonized by Spain and Portugal.
In Latin America the use of fauna with medicinal properties is a common practice since pre-Hispanic times. According to Foster [121] medical ideas and practices of indigenous peoples, along with the specific to the Spanish folklore and medieval and classical formulations have built a solid traditional medicine in this region of the world. Logically, the biogeographical differences between the Iberian Peninsula and the countries under colonization prevented the dissemination of a knowledge relate to the medicinal use of fishes at the species level. However, taxa belonging to families such as Carangidae, Engraulidae, Gadidae, Scombridae or Syngnathidae are/were used in both areas [122].
Brazil is the country where a greater number of species are used as medicines (85): 44 fresh-water species and 41 salt-water species [19]. According to a recent review [123], 77 species are consumed as food medicines. Among the fishes there documented the consumption of two genera coincides: Dasyatis, used in the Spanish medicine until the 17th century, and Gadus. In the latter case, G. morhua is the only species consumed, particularly in the treatment of furuncles. This species is also used in Brazil as a topical remedy for rheumatism and backache [19,122]. It can ensure that the Atlantic cod is a medicinal species used in force in Brazil, Portugal and Spain.
There is no doubt that the use of fishes, as a "general ethnotaxa", must be part of a cultural transfer between the New and Old World as a consequence of symbolic nature [98]. Such cultural transfer stimulated the use of certain fish species similar to those in Europe, as well as their derivatives. For example, Francisco Hernández de Toledo (1514-1587) in his book Cuatro libros de la naturaleza y virtudes de las plantas y animales de uso medicinal en la Nueva España (published in Mexico in 1615) describes the use of otoliths against kidney stones [124], also used for the same purpose in Spain. In the Argentine Gran Chaco region the venomous sting of the stingray Potamotrygon is used to eliminate the toothache [125] similarly to how the sting Dasyatis pastinaca was used until the early 17th century in Spain [36].
Likewise, in both geographical areas they are/were used dried seahorses (genus Hippocampus). In Spain, until the mid 20th century, these charismatic animals were only carried in the pocket or round the neck as amulets to prevent erysipleas and cure toothache (see Table 3). No longer are roasted and eaten. Conversely, in Brazil the longsnout seahorse (Hippocampus reidi) is among the most versatile fish species in terms of therapeutic indications [19,126]. This species is still consumed by its intake as part of different mixtures (teas, concoctions, etc.) with various medicinal plants and animals. These medicinal and/or superstitious uses put these fishes among the most traded animals for medicinal purposes. This led to the entire genus was included in May 2004 in the Appendix II of CITES, to ensure that trade is not detrimental to the survival wild populations [126].

Conclusions
Historically, fish-based therapeutics is based on a dietary usage; it has been an essential product in the care and maintenance of health from antiquity to the present. However, throughout history a wide range of pathologies have been treated through the use of these animals, and some remedies have survived to this day, highlighting especially those related to infectious and parasitic diseases, pregnancy, childbirth, puerperium and diseases of the musculoskeletal system. There is also a cultural merging, or syncretism detected in the remedies and a strong relationship exists between magic and empiricism. In the last century both were almost equally present, a period in which we also find a progressive decrease in the number of fish species used. Seven species have been documented as surviving therapeutic resources since centuries ago; the existence of a dynamic Spanish ethnomedicine has also been detected which has managed to generate new therapeutic resources in recent times. Historical ethnozoology can be a transverse axis in the history and philosophy of science; it may participate in the establishment of cultural parallels and even as ethnopharmacological research support. Despite the limited interest shown in zootherapy in Spain, it is important to evaluate it along with the rest of traditional ecological knowledge, much of which has been validated by ethnopharmacology and evidence-based medicine. In order to recover as much data as possible, it will be necessary to draw up an inventory of ethnoichthyological uses, so that it could act as an anamnesis of remedies together with the data compiled in this study. It is also important to determine the cultural significance of fish-based zootherapy and to further watch and determine how globalization and multiculturalism are influencing.