In the most scientific and biological sense, the primary difference between the cod and haddock is their species type. Both fishes actually belong to the same family gadidae, but branch out into different genus, with the haddock under the melanogrammus genus, with the cod being a member of the genus gadus. Overall, this difference in species between the cod and haddock largely accounts for the difference in appearance, eating habits, and habitat.
These fish can be very similar in appearance, but the most apparent difference between the two fishes is their lateral lines running from the head to the tail. The cod has a pale, whitish lateral line, while the haddock has a dark black lateral line, along with some blotches on its pectoral fin located as the side of the head. The haddock has a longer and more pointed primary dorsal fin, located on the fish’s back nearest the head, than that of the cod’s. The haddock’s tail has also a more concave appearance than the cod’s blunter tail-end. Both fishes also differ in color: the cod appears to have a greenish, yellowish tinge, while the haddock has a grayish, silvery shade.
Both fishes live on similar ranges, such as in the North Atlantic and the Gulf of Maine. Their depth of habitation, however, differ in that the cods live in shallower waters than the haddocks that seek deeper waters. Cods are aplenty in 5 to 10 fathoms (9.14 to 18.28 meters) deep, while haddocks populate the waters from 20 to 70 fathoms (36.57 to 128.01 meters) deep. This is probably why cods are more prone to overfishing than the haddocks. In fact, the World Wide Fund (WWF) listed the cod as an endangered species in the year 2000, and in 2010, the Atlantic cod was placed on the Greenpeace International’s “seafood red list.”
In terms of their eating habits, the cod and haddock eat similar foods such as sea cucumbers, worms, brittle stars, and mollusks. The difference is that the cod eats bigger-sized clams and crabs, while the haddocks do not. Haddocks also eat more worms than cods, probably because sea worms are plentiful near the bottom of the ocean. Cods, on the other hand, would even attempt to catch little sea ducks near the water surface.
An expert fisherman or angler may know the difference between the cod and haddock, but even chefs can detect the difference in terms of texture and text. The cod is slightly softer than the haddock when gently pressed, an indication of a difference in the meat texture. The cod meat is moister and plumper, while the haddock can have a flaky and dry consistency. The cod and haddock both taste similarly, but many cooks say the haddock has a sweeter flavor.
黑线鳕，又称“北大西洋鳕鱼”，属于鳕鱼科。
形态特征：黑线鳕有许多特征，有助于区别它及其他鳕鱼，例如它高而尖的第一背鳍、黑侧线及胸鳍上方的深色“拇指纹”。此外，它下鄂上的小触须比上鄂的触须短。它们通常聚成一大群，活动于40米或更深的水底附近，平均小于2.27千克，一般最大可达6千克左右。
产地：北大西洋。
钓法：钓海洋中的鳕鱼可在岸边用滩投法钓，或在岩石、码头及防波堤上用天然饵钓，也可以在船上用天然饵或毛钩、汲钩或引起注意的匙型饵连接饵钩来钓。鳕科鱼类中的淡水鱼江鳕是一种行动缓慢的鱼，主要在晚上摄食，可在浅水中以静止底钓法来钓。
钓具：用岸钓钓海鱼时，试试3.7米的滩投竿及强力卷线器、13.6千克尼龙线、2/0～8/0号钓钩，及一个子弹形铅锤或抓底铅锤。从船上钓海水鱼时，用13.6靠边我级船钓竿及4/0～6/0强力卷线器、3.6千克钢丝引线或尼龙线，及2/0～8/0号钓钩。用天然饵钓及毛钩钓时，用一个子弹形的铅锤。钓江鳕时，试试3至3.7米投底直感钓竿及定轴式卷线器、2.7千克单纤母线，及10～14号钓钩。
钓饵：钓海鱼有效的天然饵种类相当繁多，包括许多无脊椎动物，如蚌、海蚯蚓、蛤、竹蛏及乌贼。至于饵鱼，无论是切片或整条的鱼都值得一试，尤其是油多的鱼，如鲱、鲭、黍鲱及沙丁鱼。在人工饵中，铅头汲钩、金属汲钩及塑胶玉筋鱼皆有效。一束橘色或白色的羽毛钩装在5/0号钓钩上是极佳的船钓假饵。江鳕会吃整串的大蚯蚓或小鱼。
黑线鳕鱼是一种分布于北大西洋的底栖海鱼，作为一种被人们大量食用的鱼类，黑线鳕一直处被长期商业性地捕捞。黑线鳕很容易通过白色侧身上的黑色侧线辨别出。黑线鳕常见于40至200米深处，而且幼鱼较成年鱼偏好栖息于浅水域，它们一般生活在近大陆架或者远离海岸的冷水海域，其适宜水温为2至10℃(36°至50°华氏度)。
一般来说，黑线鳕并不是善于长距离游动的底栖鱼类，一年之内的地区性迁徙并不常见，但中短距离的寻求食物的迁移有时也会发生。成年鳕不似较年轻的鳕那样惯于洄游，但所有老幼的鳕都会有季节性迁徙。黑线鳕的食性根据体型大小、季节和地区不同而相异。举例来说，小鱼虾为幼年鳕的主要食物，而较大个体的鳕鱼则食用其他鱼类，尤其是在春季和夏季。但是，在冬季所有大小的黑线鳕一般都取食底栖无脊椎动物，如蠕虫、小型软体动物、海蛇尾及海胆。
黑线鳕是海军陆战队员鱼分布在的两边北大西洋.黑线鳕是一种普遍的食用鱼，商业广泛钓鱼。黑线鳕由黑色容易地认可侧线跑沿它的白色边，不混淆与狭鳕哪些在黑边有相反、空白线路和一个特别黑暗的污点在之上胸鳍。
黑线鳕通常被找到在40到133米的深度，但有范围一样深象300米。它在温度兴旺2°对10°C(36°对50°F)。青少年更喜欢浅水区和更大的成人深水。通常，成人黑线鳕不参与长的迁移行为象鱼苗，但季节性运动知道横跨所有年龄发生。黑线鳕主要在小哺养无脊椎，虽然种类的更大的成员也许偶尔地消耗鱼。
黑线鳕生长率显著改变了过去30到40年。目前，成长是迅速，当黑线鳕到达他们的成人大小早先更加早于被注意。然而，程度这个鱼苗对人口的再生成功贡献是未知的。
黑线鳕正处于生物学上的危险状态，从2003年开始，有必要对其实施禁渔。报告提出，对鳕鱼资源的恢复至少需要5至6年，而在生物学上则必须实施12年的禁渔。作为欧洲最重要的商业品种的鳕鱼、黑线鳕是以波罗的海和北海为主渔场，2002年欧洲鳕鱼的渔获配额为14.9万吨，在北海的渔获配额占4.1万吨，约占25%；黑线鳕的配额是10.7万吨，其中7.7万吨是属于北海的渔获配额。然而，这两种鱼的资源量都急剧下降。让鳕鱼恢复健康的再生产可能需要10万吨产卵资源量。因此，苏格兰海洋研究所长罗宾库克向欧洲渔业委员会建言迄2015年为止要采取零配额的禁渔措施。对此，以北海资源为生的英国及苏格兰全体业者强烈反对。
