Sea herring fish

The herrings are the original species of the North Atlantic, the pelagic counterpart to the cod. The great majority herring species are warm-water fishes: of approximately 190 species of herring worldwide.

Most herring species live exclusively in salt water but there are a number of freshwater species, most of them in the tropics and an equal number of anadromous species.

Herrings can be distinguished from other species by several characteristics - they are no rayed canals on the grill cover bones; lateral line pores are absent; there are keel scales the medial line of the belly.

Blueback herring 

In the United States sea herring are found in ocean waters from Alaska to the state of Washington on the West Coast, and from Labrador to Cape Hatteras on the East Coast.

Sea herring are plankton feeders, eating the various microscopic plants and animals (diatoms, larvae of various shellfish, etc) when very young and, as adults, eating small shrimp, small fish, and so on. When unmolested, the sea herring may live to an age of 20 years or more.

Herring populations may mix during overwintering and feeding seasons, but then separate during the spawning period.

Most sea herring are caught with purse seines, but some are caught with pound traps or weirs (similar to pound traps but constructed with poles and brush). Gill nets are sometimes used to catch these fish.
Sea herring fish

Notes
*anadromous are the fishes that’s spawn in freshwater but spend much of their life in the ocean.

Fatty acid consumption can reduce risk of Alzheimer's

Alzheimer’s disease is a neurological disorder that is characterized by progressive memory loss, intellectual decline, and eventually global cognitive impairment.

The brain of an Alzheimer’s patient undergoes more severe changes than the brain of a healthy person. 

Research has suggested that people with Alzheimer’s disease may have unusually low levels of essential fatty acids in their brains.

Essential fatty acids must obtain for human diet to maintain good health.

The polyunsaturated fats found in salmon and mackerel and the monounsaturated fats found in canola oil and soybean oil are high in essential fatty acids, called omega-3 fatty acids.

A diet rich in unsaturated fatty acids and unhydrogenated fat was found to protect against Alzheimer’s disease, in contrast to a diet rich in saturated fatty acids and trans fatty acids.

Saturated animal fat in the diet increases the risk of developing Alzheimer’s disease. Consumption of fish containing high levels of omega-3 fatty acid counteracts some of that risk.

The effect was still present when socioeconomic factors were taken into account, as these factors are linked to both the reduced risk of Alzheimer’s disease and the fish consumption.

A study carried out in the United States found that Alzheimer’s disease was 60% less in people that consumed about 60 mg DHA per day or at least one fish meal per week than in people that ate very little fish.

A 2008 study published in the American Journal of Clinical Nutrition reported that an increased risk of dementia was found to be associated with a higher ration of arachidonic acid to DHA and a higher ration of omega-6 fatty acids to omega-3 fatty acids, especially among subjects who are depressed. Depression is frequently associated with Alzheimer’s disease.
Fatty acid consumption can reduce risk of Alzheimer's

Fish and temperature

How important the temperature to fish? To give some idea of the important of temperature , fresh caught fish will generally last about 12 days if held in ice (temperature) at about 32°F or 0°C) whereas they will last only about 4 days at 46°F (7.8°C), a temperature sometimes found in domestic refrigerators.

Temperature is the main abiotic factor influencing the metabolic process and growth in fish. It influences the timing and duration of most life history stages.

Un-iced fish may suffer severe contractions that tear the flesh and produce an unsightly product.

The growth of bacteria and the rates of enzymatic and chemical activity are directly related to temperature.

There are at least three reasons why fish spoil so rapidly at refrigerator temperatures. Primarily, because they are readily digestible; second, because the muscle glycogen is nearly depleted during harvesting , leaving little to be converted to acid, which would act as a preservative.; finally , because the bacteria found on fish are psychrophiles – that is, they can grow well at low temperature.

Research shows that refrigerated must be maintained near 0°C for maximum quality retention.

It is well known that both enzymatic and microbiological actvoty are greatly influenced by temperature. However, in the temperature range from 0 to 25° C microbiological activity is relatively more important temperature changes have greater impact on microbiological growth than on enzymatic activity.

Among psychrophiles there is a range of optimum growth temperatures for different species , ant it is known that some of the psychrophilic bacteria found naturally on fish grow at such low temperature that they are reliably detected by standard bacteriological plating techniques.

Fish and temperature

Fish and shellfish

Humans were eating fish and shellfish long before they started cultivating plants or domesticating animals for food.

Shellfish are hard-covered , edible, mostly marine animals from two groups: the mollusks (oysters, clams, mussels) and crustaceans (crabs, lobsters, shrimp).

Fish and shellfish contain high quality protein with all the essential amino acids like red meat and poultry.

It is also low in fat and most of the fat it has is unsaturated.

Although shellfish have less oega-3 than the fatty fish, shellfish are still very good sources, better sources than the leaner fish. Shrimps, oyster and mussels are the leaders of the pack.

Generally, shellfish contain the usual amounts of cholesterol as found in meat.

Fish for human use produce largely by fish farming. It may be that the situation is beginning to change.

In some countries, several freshwater species (catfish, carp, trout, and tilapia) have been raised as a commercial enterprise for some years and milkfish have been raised for many years in the Philippines.

Oysters are now grown commercially in some areas, and the raising of shrimp in Japan is already commercialized.
Fish and shellfish