Experiments with the hatching of salmon spawn 1966-1971. [Translation from: Vann 1972(1) 86-938, 1972]

Experiments were undertaken with the purpose to find out the tolerance of different species of salmon fish in acid hatching water and if different strains of the same species differ in their response. The study was made in the Fins-river hatchery, Marnardal and the assumption tested that the salmon and trout stock from Sorland are adapted to the more acid milieu, and thus more robust in acid water than are comparable fish stocks from areas where the water is only a bit acid or neutral.

Comparison of observed and predicted dates of eyeing, hatching and swim-up for brown trout and Atlantic salmon

Scholars recently derived simple models from published data for the prediction from water temperature of hatching times for the eggs of brown trout (Salmo trutta L.) and Atlantic salmon (Salmo salar L.). A similar model to predict eyeing time for salmon eggs was obtained and used in this study, largely by analogy, to develop equations which might be used to obtain very approximate estimates of eyeing and swim-up times for salmon and brown trout. As the models were based on data for constant temperatures and some of them also had a very inadequate data base, it was desirable that they should be tested, as far as possible, against field and hatchery observations. The present report is a brief summary based on such data as have been obtained to date. None of the data sets were ideal for the purpose and the various inadequacies are discussed later in this report.

The effects of temperature on hatching and survival of northern rock sole larvae (Lepidopsetta polyxystra)

Northern rock sole (Lepidopsetta polyxystra) is a commercially important flatfish in Alaska and was recently classified as a distinct species from southern rock sole (L. bilineata). Taxonomic and vital rate data for northern rock sole are still not fully described, notably at early egg and larval stages. In this study, we provide new taxonomic descriptions of late-stage eggs and newly hatched larvae, as well as temperature-response models of hatching (timing, duration, success), and larval size-at-hatch and posthatch survival at four temperatures (2°, 5°, 9°, and 12°C). Time-to-first-hatch, hatch cycle duration, and overall hatching success showed a negative relationship with temperature. Early hatching larvae within each temperature treatment were smaller and had larger yolk sacs, but larvae incubated at higher temperatures (9° and 12°C) had the largest yolk reserves overall. Despite having smaller yolks, size-at-hatch and the maximum size achieved during the hatching cycle was highest for larvae reared at cold temperatures (2° and 5°C), indicating that endogenous reserves are more efficiently used for growth at these temperatures. In addition, larvae reared at high temperatures died more rapidly in the absence of food despite having more yolk reserves than cold-incubated larvae. Overall, northern rock sole eggs and larvae display early life history traits consistent with coldwater adaptation for winter spawning in the North Pacific.

Hatching date, nursery grounds, and early growth of juvenile walleye pollock (Theragra chalcogramma) off northern Japan*

Walleye pollock (Theragra chalcogramma) is widely distributed in the North Pacific Ocean and plays an important role in coastal subarctic ecosystems. The Japanese Pacific population of this species is one of the most important demersal fishes for commercial fisheries in northern Japan. The population is distributed along the Pacific coast of Hokkaido and the Tohoku area (Fig. 1), which is the southern limit of distribution of the species in the western North Pacific. In Funka Bay, the main spawning ground for this population, pollock spawn from December to March (Kendall and Nakatani, 1992). Planktonic eggs and larvae are transported into the bay, where juveniles usually remain until late July when they reach 60−85 mm in total length (Hayashi et al., 1968; Nakatani and Maeda, 1987). These juvenile pollock then migrate from Funka Bay eastward to the Doto area off southeastern Hokkaido (Honda et al., 2004). Many studies on eggs, larvae, and juveniles of the species have been conducted in or near Funka Bay, but little information is available on the ecology of the early life stages in the Tohoku area. Hashimoto and Ishito (1991) suggested that eggs are transported from Funka Bay southward to the Tohoku area by the coastal branch of the Oyashio Current, but there has been no study to verify this hypothesis.

Comparative study of hatching rates of African catfish (Clarias gariepinus Burchell 1822) eggs on different substrates

The hatching rates of African catfish (Clarias gariepinus) eggs on four natural substrates: the roots of Nile cabbage (Pistia stratiotes), water hyacinth (Eichhornia crassipes), pond weed (Ceratophyllum dermasum) and green grass leaves (Commelina sp.), and four artificial substrates: sisal mats, nylon mats, papyrus mats and kakaban mats, was assessed. Concrete slabs were used as control. The natural substrates performed better than the artificial ones. Pistia roots gave the best mean hatching rate of 66.2 ± 3.62%. Green grass leaves were second with a mean rate of 54.0 ± 3.46%, water hyacinth was third with 49.7 ± 3.16% and Ceratophyllum fourth with a mean of 13.0 ± 2.37%. Concrete slabs gave a mean rate of 18.6 ± 2.8%, sisal mats 18.6 ± 2.0%, papyrus 12.2 ± 1.2% and kakaban 11.8 ± 1.9%. Nylon mats were the last, with a mean rate of 4.0 ± 0.7%. The best performing natural substrates were those with the ability to float and thin fibrous roots that seemed to allow higher aeration of the eggs during incubation. The cost of using natural substrates was minimal.

Effect of different salinity levels on the fertilization and hatching of Heterobranchus bidorsalis

The success of induced spawning for the production of fish seed depends on many factors which affect hatchery conditions. This paper discusses the results of an investigation on the effects of six different levels of salinity on the fertilization and hatching of Heterobranchus bidorsalis eggs. The results indicate that spermatozoa of H. bidorsalis can survive under a wide range of saline concentrations, with survival increasing with an increase in salinity from 0 to 0.4% and then decreasing as the level of salinity increases. Survival was optimum of 0.4% saline concentration.

Low cost breeding and hatching techniques for the catfish (Heteropneustes fossilis) for small-scale farmers

The high demand for the stinging catfish (Heteropneustes fossilis) and declining wild stocks led the Centre for Aquaculture Research and Extension of India to look for methods for the culture of the species. This paper presents a low-cost, simple breeding technique developed and tested by the Centre that can be easily adopted by rural farmers.

Spawning and hatching performance of the silvery black porgy Sparidentex hasta under hypersaline conditions

Abu Al Abyad island is characterized by harsh environmental conditions. A preliminary trial conducted at the island to investigate the spawning and hatching performance of the blue finned sea bream Sparidentex hasta indicated that the fish can be successfully bred at high salinity levels exceeding 50 ppt.

Hatching cage Tower Mill, 1950

Photo of a hatching cage in Tower Mill, an unidentified location in the North West of England, UK. The image was taken in 1950. This photo is part of a Photo Album that includes pictures from 1935 to 1954.

A comparative study on the hatching of common carp eggs in hapa and hatchery (model CIFE D-80)

Common carp (Cyprinus carpio) eggs were incubated to study the efficiency of hatching in hapa and hatchery. During incubation the recorded temperature was 21-28 degree C and 20-31 degree C, dissolved oxygen 6-9 ppm. and 3-5 ppm., total alkalinity 180-250 ppm. and 28-62 ppm. respectively in the hatchery (model C.I.F.E. D-80) and hapa. CO sub(2) was totally absent in the hatchery, but recorded 3-10 ppm. in the hapa. The flow of water was maintained at 1.25 l/minute/jar in the hatchery. Under the above environmental conditions the eggs hatched in 42-51 hrs. in the hatchery and 61-81 hrs. in the hapa from egg to spawn thereby establishing the hatchery to be a better hatching system for carp eggs.

Effect of sodium bicarbonate on hatching and on postembryonic growth of Brachydanio rerio, Cyprinus carpio, Labeo rohita, Cirrhinus mrigala and Catla catla

The treatment of sodium bicarbonate at the dosage of 100 to 1000 mg/litre has been tested experimentally on the hatching and postembryonic growth of Brachydanio rerio, Cyprinus carpio, Labeo rohita, Cirrhinus mrigala and Catla catla. Lower dosages of 100 to 200 mg have been found to reduce the hatching period, yolk absorption period and improve the survival and growth of the post embryonic larvae. The higher dosages of 500 to 1000 mg has been found to reduce the hatching percentage and post embryonic growth of the larvae. The findings indicate that application of sodium bicarbonate in the hatchery and nursery management of carps in the lower dosages of 100 to 200 mg/L to improve hatching and postembryonic growth.

Effect of decapsulation on viability and hatching performance of Artemia cysts at different salinity levels

Artemia cysts were produced from the traditional solar salt works of Bangladesh through different fertilization treatments were tested for viability and hatching performance in different forms, such as processed and preserved, processed and decapsulated and unprocessed and undecapsulated. Decapsulated cysts performed maximum hatching (86.0%) in 20ppt salinity during 48 hours of incubation. The hatching percentage by the unprocessed and undecapsulated cysts were very low (12.0- 18.7%) in all the tested salinity grades.