水产专业英语概述

水产专业英语概述 Revised by Jack on December 14,2020English for Fisheries水产专业外语Editor: LIU JUNWuhan Polytechnic UniversityFeed Science Department水产专业英语概述何谓水产专业英语：用来记载水产专业文献的一种英语文体——科技英语（English for Science And Technology）简称EST。

一、科技英语的诞生和特点EST诞生于本世纪五十年代，第二次世界大战结束后不久，各国（特别是西方国家）迅速恢复国民经济生产，此时正是科技技术发展的好时机，随着科学技术的发展，科学文献以惊人的速度增长，而英语的世界光发表使用的语言，目前用英语出版的科技文献占世界总量的60%以上（85%）。

因此，科技英语应用而生，世界各地纷纷建立了科技英语研究中心，我国也在北京、上海等地建立了EST研究中心。

前面已述科技英语是英语的一种文体，英语就其文章的体裁来讲，可分为四大类：文学文体，政论文体，应用文体和科技文体。

科技英语与普通英语或基础英语没有本质的区别，语音、词汇、语法是构成语言的三大要素。

以语音而论，科技英语没有独特的语音的系统；以词汇而论，科技词汇是英语的组成部分；以语法而论，它虽具有一定特色，但仍未摆脱英语语法的法规。

（一）科技英语在词汇上的特点1、专业词汇出现的频率低根据美国和伊朗两国的科技英语专家共同了一次科技词汇的词频调查，发现专业词汇出现的频率最低，而功能词（冠词、介词、连词）出现的频率最高。

我统计一下，Lesson One 共有单词211个，专业词汇出现27次，约占整个词汇的%。

2、词义专一在文学英语中，一词多义和一义多词的现象很普遍，也正是因为这样，作家才能写出生动感人的作品来。

而科技英语要求叙事明了，说理准确，所以科技工作者在表达一个科学概念时，都会不约而同地选择同一个词汇（指科技词汇），其原因是由于科技英语的词义专一所致。

大家可以打开科技英语字典，就可以发现很少有一词多义的单词。

在科技词汇中另一个特点就是词形越长，词义越专一。

例如：mammal哺乳动物，shrimp虾，swim-bladder鳔，plankton浮游生物，climbing fish斗鱼，pneumonoultramicroscopicsilicovolcanoconiosis火山爆发超微粒尘肺病。

3、科技词汇多源于希腊语和拉丁语根据美国科技英语学家Oscar的统计，在一万个普通英语词汇中，约46%的词汇源于拉丁语，%源于希腊语，专业性越强的科技英语词汇中，这种比率越高。

其原因是拉定语和希腊语的世界成熟最早，最发达的语种，词形、词义稳定。

4、广泛使用缩写词在物理、化学专业中，缩写词用的多，水产上用的不多。

据统计，科技英语的缩写词大概有2-3万个。

5、前后缀出现频率高例如在Lesson One 中ichthyology=ichthy+ologyphytoplankton=phyto+planktonosteichthyes=oste+ichthyes对于一个科技工作者来讲，要求至少掌握50个前缀和30个后缀，这对扩大词汇量，增加阅读能力，提高翻译速度是大有裨益的。

（二）科技英语在句法上的特点1、长句使用多2、广泛使用被动语态英语与汉语不同之一就是英语中被动语态使用较多，而在科技文献中被动句显得更多，据统计，在科技英语中大约有1/3的动词用于被动语态。

其原因是科技英语描写的是科学技术和自然现象，要求作者注重事实和客观规律，不带个人感情色彩，因此写作时避免使用第一人称而同被动语态，同时使用被动语态可使描写对象位置突出。

3、普遍使用形容词短语作后置定语例：sufficient to 足够的， suitable for 适于，difficult to 难，capable of 能力。

4、动词非谓语形式使用频率高动词非谓语形式又叫为非限定动词，包括不定式，动名词，分词三种。

（三）科技英语在修辞上的特点1、时态运用有限英语共有十六种时态，而在科技英语中只有九种。

描述自然规律或事实，论述理论用一般现在时，叙述过去的研究上用过去时，间或用现在完成时；对于课题是研究展望用将来时。

除此之外，还可用进行时，过去完成时，将来完成时，现在完成时，过去将来时。

2、修辞手法较单调描述科学的语言注重事实和逻辑，往往以图表、共市数学来表达可写概念。

一切文学修辞手法（夸张、明喻、隐语、借喻、拟人，对照等）都会破坏科学的严肃性。

3、逻辑——语法词使用普遍（1）表示原因：as, due to, because of, caused of（2）表示转折：but, however, nevertheless, yet（3）表示秩序：so, thus, therefore, moreover（4）表示限制：only, except, unless, besides（5）表示假设：suppose, supposing, assuming, provided二、科技英语的翻译（一）何谓翻译翻译是把一种语言文字的意义用另一种语言文字表达出来。

翻译本身不是一门独立的创造性科学，但它即带有创造性，又具有科学性。

它是用语言来表达一门艺术，是科学的再创作。

翻译到底是否带有创造性和科学性翻译过文章的人都有这样一种体会，读懂一篇英语文章并不难，但要把它翻译成中文，用恰当的中文完全把它表达出来却并不是一件很容易的事。

例1：It is a cold winter这个句子一看就懂，但往往容易把它译错，译作“这是一个寒冷的冬天”。

汉语“冬天”的含义是季节，而不是指冬天的一天。

译作“这是寒冬的一天”，也不对，因为cold 修饰的不是winter, 而是day。

译作“这是一个寒冷的冬天的一天”，意思才对，但句子很别扭。

懂得翻译技巧，便会运用“抽词法”将它译成：冬天，一个寒冷的日子。

例2：All substances are not good conductors照字面上译：“所有的物质都不是良好的导体”。

All 与否定词No 一起使用，并不是表示全部否，而只是表示部分否定，因此句子应译成：“并不是所有的物质都是良好的导体”。

所以翻译确实是一门艺术，是一门即具有创造性，又具有科学性是艺术，是对原文的再创造，是用另一种语言对原意是正确表达。

（二）我国翻译是历史和翻译是标准我国的翻译史是以佛教经典汉译为发端延续到今，历是仅两千年。

最早主要采用照本直译法（所以经书难读，难背），后秦时该为意译，译文流畅易懂。

唐代采用直译，意译并用，译文准确晓畅。

直到清朝末年，翻译家严复提出“信、达、雅”的翻译标准，由于他过分的强调“达、雅”，所以有些译文他自己也承认是编出来的，而不是翻译出来的。

后来鲁迅先生在严复的“信、达、雅”[信指忠实，达谓之通顺，雅意为修辞]是基础上提出“信”和“顺”两条标准。

“信”就是“忠实”，忠实于原文是思想内容和风格，而不是保存原作形式，更不是逐字逐句的死译；“顺”是指“通顺”，疑问的语言形式要符合译文的语言规范，做到通顺易懂。

（三）翻译是过程翻译的过程是理解和表达的过程。

1、理解翻译首先是对原文的理解，必须对所译的每一个词，短语，句子读懂，了解其含义。

2、表达表达是在正确理解原文的基础上，运用“直译”和“意译”相结合的放大将原文是内容表达出来。

（1）什么是直译既忠实原文内容，又忠实于原文形式是翻译就是直译。

只有原文结构形式与汉语的结构形式一致时，才能直译。

例：Most living fishes are bony fishes, members of the class Osteichthyes.大多现存的鱼类是硬骨鱼类，属硬骨纲。

（2）什么是意译在忠实原文的前提之下，摆脱原文结构的束缚，使译文符合汉语的规范。

原文结构形式与汉语的结构形式不一致时，采用这种方法。

例：Water is highway, byway, communications medium, nursery playground, school, room bed, board, drink, toilet, and grave for a fish.水既是鱼类的交通道又是它们传递信息之媒介，既是鱼类抚养、玩乐、学习、生活的场所，又是它们饮食、排泄和葬身之地。

Lesson OneWhat Fish AreFish are cold-blooded animals, typically with backbone, gills, and fins, and are primarily dependent on water as a medium in which to live. Their study composes the pure and applied aspects of the science of ichthyology. Obviously not included in this field of learning are mammals, such as whales, seals, and porpoises; reptiles, such as aquatic turtles; and invertebrates, such as clams, shrimp, and lobsters (“shellfish”).Fishes are the most numerous of the vertebrates, with estimates of around 20,000 recent species, although guesses range as high as about 40,000. In contrast, it is commonly assumed that bird species number about 8,600, mammals, 4,500 (of which living man is only one ),reptiles, 6,000, and amphibians, 2,500, Thus, not only are there many different fishes but they come in many different shapes and sizes. Included are pygmies such as the American percid least darter (Erheostoma microperca) which matures sexually at a length of 27mm, and a dwarf pygmy goby (Evlion) of the pacific which breeds at sizes less than 15mm. There are giants, too, such as the whale shark (Rhincoden), which has been judged to attain lengths near 21 m, and weights of 25 tons or more. Most fishes are torpedo-shaped, but some are round, others are angular.词汇backbone 脊椎骨 porpoises 海豚breed 繁殖 pygmies 侏儒类（微小鱼类）gill 鳃 seal 海豹ichthyology 鱼类学 shellgish 贝类lobsters 龙虾词组American percid least darter 美洲小河鲈cold-blooded animals 冷血性动物torpedo-shaped 纺锤形的毫米millimeter厘米centimeter分米decimeter米meter公里kilometerLesson TwoHow Fish LiveWater is highway, byway, communications medium, nursery playground, school, room bed, board, drink, toilet, and grave for a fish. All of the fish’s vital functions of feeding, digestion, assimilation, growth, responses to stimuli, and reproduction are dependent on water. For a fish, the most important aspects of water are dissolved oxygen, dissolved salts, light penetration, temperature, toxic substances, concentrations of disease organisms, and opportunity to escape enemies.Although humans are able to absorb oxygen directly from air through the vascularized walls of the lungs, few fish have lungs or other devices for utilizing oxygen from air. Most fish, including those with lungs, depend mainly upon gills to extract oxygen dissolved in water. Fish can not live long in a habitat rare or deficient in dissolved oxygen any more than humans can survive in the upper atmosphere or the space beyond unless they carry an oxygen supply with them.The pasturage that the sea, lake, and steams afford to fish depends initially on the penetration of light into water, even as growth of grass on the open range relies upon the sun.T he “grass” of the waters is microscopic plant life-diatoms and algae, collectively termed phytoplankton.The beginning of life leading to fish production is generally in the bodies of the phytoplankters. They utilize light energy and dissolved carbon dioxide to manufacture organic matter that eventually becomes food for fish. Besides proving energy for food production for all fishes, light is also known to trigger mechanisms of reproduction, growth, and many kinds of behavior, including that of feeding.Unwanted materials such as toxins produced in nature and pollution from human activities are serious menaces to fish life. The aquatic habitat provides no places of escape from damaging substances in solution. The threat to fish of water-borne toxic materials is comparable to that of air-borne pollutants to human beings. Although fish are able to detect many such chemical contaminants, they are often unable avoid them.Like all animals, fish have a very full complement of diseases with which to contend. Many of these are due to external agencies; others arise internally. From outside come viruses, fungi, bacteria, parasitic protozoan, worm, crustaceans and lampreys. From within arise almost all the common organic and degenerative disorders that plague man himself. Included are cancer, rickets, and degeneration of the liver, blindness, and a host of developmental anomalies such as Siamese twinning and spinal flexure. And even if not killed by a disease or disorder such as the foregoing, the fish must still survive periodic adverse chemical conditions in water, predators, and the capturing devices of fisherman.词汇diatoms 硅藻类 phytoplankton 浮游植物（总体）lamprey 海七鳃鳗 rickets 佝偻病pasturage 牧场 vascularized 脉管化的phytoplankter 浮游植物（个体）词组degeneration of the liver 肝功能退化host of developmental anomalies 大量畸形发育Siamese twinning 连体双胞胎spinal flexure 脊柱螺旋卷曲Lesson ThreeThe Breeding of FishFish have developed many different ways for gaining nearness of sperms and eggs to each other in order to facilitate and insure their union. Outstanding among these ways are the nicely timed relations of the various reproductive functions. In the prolific open-water spawners, for example, the millions of eggs do not all mature at one time; just enough mature in each batch so that at the final stage of the eggs, the female is not too greatly distended with the enlarged sex products. If all ripened simultaneously, they would occupy a space much larger than the parent fish, so batches are timed in ripening to accommodate the parent. Many fishes have avery short breeding season, occurring only once a year as we saw, yet the males and females are on fully ripe condition at the same instant and both then are capable of exhibiting their complex breeding reactions. The secondary sexual characteristics and accessory structures which are used in courtship, clasping, or intermission develop simultaneously with the reading of the primary sexual products.Perhaps the most famous case of accurately timed relationships in reproduction is in the palolo worm which swarms to the surface of the open seas once a year at a certain phase of the moon to breed. A few fishes show similar marvelously timed relationships for breeding. The best known of these is the grunion (Leutrsthes tenuis) of the California coast. This fish spawns just after the turn of high tide at certain times of the year. It spawns almost literally out of water, as far up on the beach as the largest waves will carry it at this time of high tide. It deposits eggs and sperm in pockets in the wet sand at just such a time and in just such a position that the eggs are not likely to be washed out by wave until two weeks or a month later at the time of the next high tide. At this time the waves come up on the sand again and when they hit the places where the nests are deposited and stir up the sand, the young hatch almost instantly and go to with these waves before the tide can recede and make it impossible for them to do so. This is certainly a remarkable instance of timed reproduction as well as development and hatching. Regarding timed relationships, we should think that somewhere in a continent such as North American, some fishes are spawning at almost any time, because of the influence if latitude and altitude, as well as individuality of species and races or varieties that compose them.Most fish species have definite seasons for spawning as a part of their timed reproductive relationships, and are generally grouped as follows. Warmwater fishes are summer spawners and cold water fishes, fall and winter spawners. Species tolerating intermediate temperatures are generally spring spawners. Some tropical species spawn the year around. Fixed spawning seasons are roughly correlated with the developmental period that the fish require. Warmwater fishes (such as the black basses and sunfish, Centrarchidae) use only a few days to hatch and emerge into an environment generally favorable to growth and survival. Several months may be required for a char (Salvelinus) or a whitefish (Coregonus). Some trout (Salmo), at a mean temperature of 50 F (10℃), may average around 50 days for their developmental period. The whitefish (Coregonus clupeafoumis), at a temperature in the low 30 F (1℃), may take as much as 130 to 150 days for development to hatching. Both seem to be timed bring the young forth into conditions favorable to them. Timing of reproduction also makes it possible for more than one species to use the same breeding grounds in a calendar year. Thus in American streams that both occupy, spring-spawning suckers (Catostomus) may use the same nest (redd) sites as fall-spawning brook trout (Salvellinus fontinalis).Timed relationships, no matter how good, would not be very useful to a fish if it could not recognize a mate of the opposite sex when present. When a scientist is sexing fish he uses such characters as structure, form, and color as describe previously. With live fish, he may also use behavior. Fish themselves are also aware of form, color, and behavior when recognizing theirmates. An outstanding experimental study of the value of these attributes for sexual recognition to fish is that by Tinbergen, who has demonstrated all of these points by observing sticklebacks (Gasterosteus) in aquarium.In addition to the evolution of timed relationships, and abilities in sexual recognition, there have development among fishes several useful devices for insuring either external or internal fertilization, for external fertilization, proximity of two individuals of the opposite sex for spawning is the most common means employed. Actual pairing and some form of holding (amplexus) are sometimes used as a special development of proximity. In pairing, some fishes come side by side in actual contact and simultaneously emit eggs and sperms, and in other instances the male twists his body around that of the female, in a semicircle, or even in a corkscrew spiral for a fish with a much-elongated body such as a lamprey (Petromyzonidae).词汇amplexus 抱合 species 种char 湖红点鲑 stickleback 棘鱼grunion 银汉鱼 sucker 胭脂鱼races 亚种 sunfish 太阳鱼redd 专指鲑鳟鱼类的鱼巢 varieties 品种spawner 产卵的鱼 whitefish 白鲑词组black basses 黑鲈brook trout 溪红点鲑palolo worm 沙蚕Lesson FourTropical Aquarium FishTropical aquarium fish come from many different parts of the world. These include the large land mass of Asia from the Bosporus to China and from northern India to the islands of the Indian Ocean; and further east, Australia with its relatively restricted fresh waters; Africa, increasingly important to the tropical fish trade; the giant River Amazon and its tributaries; and finally Central America, Mexico and Florida.Wherever the fish come from, the aquarist should always try to find out all he can about the living conditions of the fish in the world because they are so varied. For instance, the tropical waters of southern Asia present many different conditions, from the sunshine of India to the damp, humid conditions in the island of the east Indonesia. There are dark, muddy ponds and ditches, paddy fields with their interconnecting drainage channels, often in low-lying areas, but there are also mountain streams with clear, fast-flowing water, and shady rivers in jungle country. There are just a few of the habitats, which support the rich fish population of tropical Asia.Two main fish groups are particularly well represented in the fresh waters of Asia. These are the barbs and loaches (Cyprinodonoidae) and the labyrinth fish (Anabantidae). The tropical barbs are closely related to many cold-water fish in Europe and North America: these include the minnow, roach, carp, and chub.The group of labyrinth fish contains a large number of brightly colored fish, most of which are easy to breed and thus well suited to the aquarium. It is believed that the first tropical fish imported to Europe was one of these labyrinth fish, now known as the paradise fish. It caused quite a stir when brought to France from China in the 1870s, and was soon bred in Paris by a Frenchman named Carvonnior.Labyrinth fish come from some of the warmest parts of the China, India, Sri Lanka, Thailand, Malaya and Sumatra. In their home range these adaptable fish live mainly in shallow, sun-drenches water of all kinds, such as ponds and pools, ditches and paddy fields. Such water is very poor in oxygen and is often extremely cloudy but the labyrinth fish have evolved the means to survive in these unfavorable conditions. They have an accessory respiratory organ, know as the labyrinth (hence their name), situated in front of the gill chamber. From time to time the fish swim to the surface in order to take in atmospheric air, which passes to the labyrinth and is taken into the blood system. In this way the oxygen deficiency in the water is made up, and the fish are able to survive in waters which would be lethal to other vertebrates. Some labyrinth fish have also developed very elongated, filamentous ventral fins, which serve to sense food in the water.However, by no means all labyrinth fish come from such unfavorable waters; some species even live in the clear streams of the mountain ranges, and they are found in enormously varied waters. One of the group, the true climbing fish (Anabas testudineus), can even leave the waters when they start to dry up and move overland to reach other waters.Another labyrinth fish, the small fighting fish (Betta splendens), which comes from Thailand, is much valued by the local inhabitants for its bright colors and its fighting ability, and by selective breeding the Thais have increased its natural coloration. The males of the species, which swim around like aquatic butterflies, displaying their exaggerated fins, are put together in couples to fight, and vicious contests take place. Old Thai families are proud of their breeding stock, and conceal the secrets of their breeding methods.Fighting fish have been introduced into aquarium circles in Europe and elsewhere, at first in the original wild form, and subsequently as the beautifully colored selected forms known as veiltails. New varieties, even more spectacular, are being developed all the time.词汇Aquarist 水产养殖者 loaches 泥鳅（这里指鳉科）barbs 鲃属中色彩鲜艳的种类 minnow 鱼岁boastfully 自夸地 paradise 攀鲈科Bosporus 博斯普鲁斯海峡 roach 拟鲤chub 侧带臼齿鲤 tributary 支流exaggerated 夸张的，炫耀的 veiltail 一种观赏鱼的名字labyrinth 迷走器或鳃上器Lesson FiveA Colorful World under GlassA visit to a public aquarium introduces us to an amazing, colorful and almost dreamlike world, one which moves constantly behind the clear glass of the huge tanks, the glowing, and sometimes iridescent (colors of the fish catching the light as they make their slow and majestic movements. Here you are in an underwater world; the other visitors, irrelevant, are perceived only dimly as shadow-like figures in the darkened hall.Those who know little about fish will be surprised by the incredible variety of their shapes and sizes, although the majority may be the torpedo-like shape one normally associates with fish, others are long and eel-like; some are flattened, almost as though compressed from above; and a few are even disc-shaped. The coloring, too, is almost unimaginably varied from dull brown to rainbow hues and so unimaginably are habits of each individual species. Some, like the cichlids, swim around actively herding and protecting their young, some swim in shoals, but others are quite solitary, often appearing momentarily and then retreating to a favorite hiding place.On a first visit is almost impossible to comprehend underwater world, but such a visit will often fire the imagination and awaken an interested in fish, too, there are often television programs about fish in the wild; there are books on fish and their habits; and on a more mundane level, schools often have aquarium tanks in their biology rooms, though usually quite small ones. Last but not least, some people’s enthusiasm is aroused simply because they see a tank in the living room of a friend, of a doctor’s or dentist’s waiting room. The beauty and feeling of tranquility imparted by aquarium tanks, even small ones with a few inhabitants, often makes people think wistfully of having such a display on view all the time, in their own homes.词汇cichlids 丽鱼科 mundane 世俗的、宇宙的herding 集群，牧食 shoals 鱼群iridescent 彩虹色的 tranquility 宁静multiplicity 众多 wistfully 渴望地、沉思地词组living room 客厅waiting room 候诊室Lesson SixLakesAlthough to the casual observer, lakes may seem to differ primarily in size and depth, scientific study has disclosed countless other points of difference. Many of these differences are critical determinants of the presence, absence or abundance of fishes. Foe example, the fish-carrying capacity of a lake varies with the character of its basin, fertility of water, the age of the water body, and changes in the kinds of fish or in the relative abundance of certain kinds and size of fish. Carrying capacity has been related to a morpho-edaphic index and specific conductance of the water.Lakes have been variously classifies according to evolutionary state and to direction of evolution. Although they are not all-inclusive, four basic types of lakes are recognized generally in the literature of limnology-oligotrophic, eutrophic, mesotrophic, and dystrophic.Oligotrophic lakes are most often deep, cold, and low in nutrients and in population by plants-especially seed plants. There are many different species but few individuals of organisms, thus a high diversity of results. These species are distributed to great depth throughout the water column. The most characteristic fishes of such lakes in the North Temperate Zone are coldwater and deepwater salmons, trouts, and whitefishes (Salmonidae). Lakes of this type undergo ecological succession into the eutrophic type; this process of aging is termed eutrophication. Eutrophic lakes succeed into ponds, swamps, and marshes. Deepwater salmonids are absent or disappearing, as the lakes become shallower, warmer, and progressively more highly organic and occupied by larger aquatic plants. In the North Temperate Zone, common fishes of eutrophic lakes include many different kinds of minnows (Cyprinidae) and the walleyes (Stizostedion), pikes (Esox), perch (Perca), and some catfishes (Ictalurus; Silurus). A mesotrophic lake is one in the middle stage between eutrophic and dystrophic when amount of organic material cycling in the lake is increasing. Dystrophic lakes too are shallow but are head toward becoming peat bogs. Their highly organic nature often renders them at least seasonally devoid of oxygen and thus of fish. Representatives of the fishes that may occur are the mudminnows (Umbridae).To whichever of the four forgoing or other categories a group of lakes may belong temporarily each lake may still differ greatly in its area, depth, volume, bottom contour, shoreline regularity, and other features. All of these physical features have some relation both to the kinds and the abundance of fishes that may be present.词汇mudminnows 荫鱼科 pikes 狗鱼perch 鲈 walleyes 大眼狮鲈词组ecological succession 生态演替morpho-edaphic index 湖泊形态——土壤学指数peat bogs 泥炭，泥沼specific conductance 电导率Lesson SevenEcological FactorsEnvironmental forces that impinge on the lives of fishes are many, complex, and interrelated in their effects. We will single out a few for illustration.TemperatureTemperature is a factor of wide and varied significance. Generally, with in the range of temperatures that can be tolerated by the fish, the effects are for vital processes to be accelerated by warm temperatures and decelerated by cold ones. Temperature extremes or sudden changes are often lethal. Elevated, sublethal temperatures may induce aestivation, and depressed ones, hibernation. Precipitation and evaporation in the hydrologic cycle are thermal phenomena. Freshwater fishes, marine species that use the freshwater habitat for growth, and brackishwater fishes are dependent on this cycle for the supply of water in which they live.Within bodies of water, temperature may determine success of a species as well as its distribution. Within the geographical range of trouts of the family Salmonidae, waters are commonly classified thermally as cold (inhabited by trout) or warm (intolerable to trout). In lakes of the Temperate zones, when stratified thermally in midsummer, coldwater fishes such as the trouts (Salmo), chars (Salvelius), whitefishes (Corgonus) remain in deep water in or beneath the thermocline (the hypolimnion) and the warmwater fishes are restricted to the shallow upper warmwater layer (the epilimnion). The thermocline is a thin layer of rapid temperature decline demarcated in the Temperate zones by a change in temperature of 1℃ for each meter of increase in depth. Low temperatures bring covers of ice to lakes in the Temperate and Arctic zones in the winter, and the growth of fishes is slowed or stopped in this season. Just before the ice covers a lake in the Temperate Zone in the fall and, again just after the ice leaves in the spring, a condition of homothermy is reached from top to bottom. This condition enables deep thermal and wind-induced circulation of such a lake (and of parts of the oceans) distributing nutrients and flocculent bottom materials from the deep to the very surface. Dissolved oxygen from the surface is mixed through the water column during this event. In super-cooled streams, ice may form on the bottom to destroy or occur out fish food organisms. Temperature of water can be an important detective influence in the migrations and movements of fishes. As a result of correlating temperature with the ranges of fishes, zoogeographers have developed isothermal of fish distribution. Limnologists have long attempted to classify lakes in the basis of their thermal characteristics. The most widely accepted classification has three major categories: Polar lakes with the surface temperatures never over 4℃ ; Temperate lakes with the surface ranging both above and below 4℃; and tropical lakes with the surface temperatures always over 4℃.It may be concluded that not only are fish temperature sensitive, but that those capable of movement generally seek what may be termed preferred temperatures. Within the range oftolerable temperatures fish continually move about as if to seek the temperature that is optimum for the vital activity of the moment.LightLight is another ecological factor of importance in the lives of fishes. Direct effects are through vision but there are many indirect ones as well. Coloration of the integument at any given time is a direct function of quality and quantity of light. Light also triggers and directs migrations and movements, has a timing role in reproduction, and influences rate and pattern of growth. Light also determines the kinds and amounts of food available for fish and is of course the direct energy source for the first photosynthetic link in the food chain of all fishes. The region where light intensity is sufficient for photosynthesis is referred to as the trophogenic or euphotic zone and extends downward to some 200m in clear seawater.CurrentsCurrents are physical factors in the lives of both flowing and standing-water fishes. At the surface, water movements tend to equilibrate air and water temperatures. Through circulation, they also tend to homogenate temperature and chemical factors in the water. Forced mixing by wind moving across the surface moves the water molecules and causes turbulence or waves. When turbulence at the surface comes into contact the water layer beneath, a current in the opposite direction is set up the lower layer. Such currents produce turbulent internal eddies which lead to vertical interchange of water particles (intermixion). This interchange is known as eddy diffusion. The cutting action of currents along stream banks and shores continually alters habitat locally, dislodged materials are transported for deposition elsewhere to effect change there. Turbidity resulting from erosion may effect adaptations (as in the eyes) of fishes but it may also be lethal or it may greatly reduce chances for survival by sedimentation of feeding or spawning grounds. It also accelerates the rate with which water absorbs heat from sunlight.Currents within stream systems typically change from fast in the headwaters to sluggish at base level with accompanying change in fish species. Generally, the stronger the current the more depauperate the fish fauna. The development of streamlining and holdfast organs among fishes is an obvious response to current. However, even as gradient in streams is an ecological factor for fishes, so are the shape, depth, configuration, and composition of the bottom of standing waters.Dissolved OxygenDissolves oxygen is required for respiration, the release of energy from food. In unpolluted streams and in the surface of lakes, ponds and the oceans the water is unpolluted streams and in the surface of lakes, ponds and the oceans the water is normally saturated with oxygen for its given temperature. It may, however, fall beneath the minimum few parts-per-million requirements of fishes at the sources of springs, and seasonally in stagnant bottom water of standing bodies. Oxygen by also be deficient over highly organic bottom deposits or in waters polluted by organic wastes such as domestic sewage. When large alga blooms die due to a few cloudy days, extensive fish kills (summer kill) may result because of decomposition。