Atlantic Herring (distribution, character and biology)
Norwegian spring spawning herring (NSSH, Clupea harengus) is one of the family from Clupeidae which are distributed over wider areas and one of the most abundant species in the world ( Nakken, 2008). Since NSSH playing an important role for Norwegian economy, the stocks was been highly exploited for commercial purpose which come out with bad impact to the ecosystems. Furthermore, changes in environmental condition also can be recognizing as a factor why NSSH species should be considered in order to well manage the resources.
Nowadays, the distribution and abundance of herring is greatly developed. The stock is composed by two main branches, from Iceland and Norway, also stated as Atlanto-Scandian spring herring according to Johansen (1919). The name changed to Atlanto-Scandian herring after the inclusion of the Icelandic summer-spawning herring. According to Atlantic Herring (website: http://www.gma.org/herring/biology/what/default.asp), female herring can produce around 20 000 to 50 000 eggs the whole of their life and the good eggs has more a less 20% portion of female's body weight. The fertilized eggs will take around 7- 10 days to become larvae, and this is depending on environment condition such as temperature.
The eggs and its development
Fish populations which from both farmed and wild, are dependent upon the production of good quality eggs. Poor egg quality is one of the major problems in the expansion of aquaculture of both marine and many freshwater fish species. "Egg quality can be defined as the egg's potential to produce viable fry" (Kjrsvik et al., 1990). For fish farming industry, "good quality of eggs have been defined as those exhibiting low mortalities at fertilization, eyeing, hatching and first feeding" (Bromage et al., 1992).
There are lots of factor that may affect the quality of egg itself. The previous study was came out with some example of factor that can be categorized as a factor, lead to the quality of eggs; which are the quality from female's side , environment condition (temperature, salinity and so on) and also time for spawning (see reviews by Kjrsvik et al., 1990; Bromage, 1994; Brooks et al., 1997). While Kjrsvik et al (1990), suggested that assessment at the early stages of cleavage (normal blastomeres) of the egg can be as a indicator tin order to evaluate the quality of eggs. This suggestion was supported when Shields et al., 1997 doing a study on Atlantic cod, turbot and halibut. The observation from the cleavage in the earliest stages is a good criterion since development of eggs was related with hatching rate and viability of yolk sac.
There's a study which s focus on marine species such as on Salmonid (Battle,1944; Gorodilav, 1996) and model systems such as zebrafsh (Doniorerio (Hamilton-Buchanan), Hisaoka and Battl, 1958; Hisaoka and Flirt, 1960; Kimmel et al, 1995), medaka (Oryzias latpes) (Temmck and Sclegel). On the other hand, there was a studied which has been done related to Atlantc herring eggs (Clupea harengus), (Almatar and Baley, 1989; Blaxter,1967 and Blaxter and Hampel, 1963) but only a few study was done related to embryonic development for Atlantic herring. The drawng of development for Atlantic herring was done by Kryzhanovsky, 1956 and Klinkhardt, 1984.
A simple staging series is a tool that has been produced in order to describe the development of embryos. A stage can be defining that, device that can approximately locate a part of development or series. There were two way how to staging the fish eggs which are by numbering the stages or a number of periods with different development description.
Growth and survival of the larvae
Effect of oil to fish eggs and larvae
Nowadays, there is an important issue that has been discuss which is related with oil contamination in the Sea off Northern Norway. These areas are considered as an important area for the conservation of marine ecosystems and especially vulnerable to the effects of man-made pollution. One of the fish species which is believed exposed to oil contamination is herring which has motivated researchers to explore more into herring. Due to this issue, oil spills may affect marine life in Northern Norway. Based on previous study on several teleost fishes, there is a toxicity of oil and its substance in fish species (Anderson et al 1974; Rice et al 1987) and it has been shown to cause changes in body structure and histopathological and genetic damage in larval and juvenile fish [Brown et al 1996], [Carl, 1987], [Heintz et al 1997] and [Hose et al 1996].
On the other cases, there are lots of examples where accidental discharges of oil to the marine environment occurred; The Exxon Valdez oil spill occurred in spawning areas of Pacific herring in Prince William Sound (PWS). Thus most or all of the life stages of the herring in PWS may have been exposed to oil following the March 1989 spill. There have been intensive studies on the effects of the oil spill on herring from PWS following the Exxon Valdez disaster. Due to the spill, Marty et al.1999, had sampled the adult herring and the result showed that there were histopathological effects on the adult fish with viral hemorrhagic septicaemia virus (VHSV).
Marty et al. (1997) also observed differences between larvae that were taken from oiled sites and un-oiled sites. Larvae from oiled sites are shorter than larvae from un-oiled sites. Due to this, it can be said that larvae from oiled sites had a slow growth since they took less food compare to un-oiled site's larvae. This study was supported by McGurk and Brown (1996), where they estimated the mortality of eggs and larvae between both sites; oiled sites and un-oiled sites. The results showed that the egg and larval mortality from un-oiled sites is two times less than oiled sites. These mean that the eggs and larvae from unpolluted sites have a higher growth compare than polluted sites. Spaulding et al. (1985) and Foyn and Serigstad (1987) found that there are a lot of effects on fish larvae due to oil contamination. These vary in a complicated interaction of factors; larvae stages development, spread or distribution of spawning, the place of spills, duration of larvae exposed to oil contaminated and environmental factors such as temperature and salinity (Rice et al. 1979).
Maternal and paternal effect to eggs and larvae
Maternal effects can be defined as comprising "a class of phenotypic effects that parents have on phenotypes of their offspring that are unrelated to the offspring's own genotype" (citation:Bernardo 1996). It's believed that, investment of reproduction from males and females may affect to maternal. It's require enough nutrition for a proper development and survival of fish and this can be seen by measure the morphological and biochemical condition of the offspring. This proved that, maternal investment has a higher impact to fish when compared with paternal effect. Moreover maternal also has a power to influence changes in early life history traits (ELHTs) (Hinckley, 1990; Buckley et al., 1991; Trippel et al., 1997).
From the previous study, a few factor why fish have a variation size and quality of eggs has been categorized, which are included age of the female fish, size and condition of the maternal. All of these factors will lead to hatching rate of the larvae (Blaxter and Hempel, 1963; Kjesbu et al., 1991; Chambers, 1997). In order to know which one will give an impact to the larvae fish either from males or female, it is important to observe the eggs size (Rideout et al., 2004).
Nowadays, there is a few studies have been done which related to the parental effect. This study was focus on parental effect such as metabolic rate, which together with feeding rate strongly influence the growth rate of a fish larva (Jobling, 1985; Kirboe et al., 1987). The growth rate of an individual larva has important consequences for its chances of survival but, obviously, it can only be determined in the period following hatch at which time environmental effects potentially mask or confound any parental effects. Since metabolic rate influences growth rate it would perhaps be better to measure effects directly on this trait, but this has proven difficult for early life stages and, once hatched, metabolic rate is also very prone to environmental influence (Huuskonen et al., 2003).
The relationships between parental effects, temperature, egg size, and larval size and survival are well characterized in herring for a number of different stocks (Panagiotaki & aGeffen 1992, Morley et al. 1999 ). In general, size at hatching, larval growth, and larval survival are all positively related to egg size. Egg size in herring is determined by maternal investment in the yolk reserves, such that bigger eggs have more yolk. However, this makes herring larvae particularly vulnerable to pollution through contamination of the yolk. In such a scenario, larger eggs will in fact carry a larger burden of contaminants. The larvae hatching from larger eggs in this case will receive higher doses, which may affect their growth and survival.
Objective of present study
Materials and methods
The herring's adult was being exposed to oil polluted with different concentration. The eggs which already fertilized with sperm were remained on glass plate and keep t in each bucket which being supplied with good water flow and Oxygen. The herring were monitored by photographed every each plates in order to identified their stages development. When the eggs were already hatched, a few of larvae from each bucket randomly being measured their weight and length in order to examine either the combination of different parents' effect the larvae or not. Percentages of hatching rate also take into account.
Place and time experiment
The experiment was conducted at HIB, University of Bergen. This study was divided into two phase: first experiment was done on February 2009 and followed by second phase which was done on March 2009. For both phases, it's taken 19 days each.
Source of fish
The herring which has been used was taken from Matre. The adult fish was exposed to four treatments which have different concentrations: control, low, medium and high concentrations of oil contaminated. For medium and high concentrations (first phase), we used 13 females and 12 males. However for control and low treatment (second phase), we used 10 females and 8 males. Ripe gonads were removed from all the fish and place on a bottle. Gonads were returned to the laboratory in HIB. After that, the eggs were spread thinly onto glass plates and fertilized with sperm.
Incubation of eggs
The herring eggs which remained on the glass plate with different parental combination were maintained in large tank with good flow through of clean water. Each tank was supplied with Oxygen and maintained water temperature at 80C. For phase one, 5 tanks were used which divided evenly between 76 large plates and 40 small plates fertilization. While for phase two, only 4 tanks was offered with 12 large plates and 33 small plates fertilization. Phase two was less than phase one and this happened due to the gonad which was not so ripe.
The eggs were photographed by using digital camera, Olympus which mounted to stereomicroscope. Randomly, a few of eggs picture, were photographed from each plate by putting them in a tray and place on stereomicroscope stage by using two different magnification which was 0.63X and 2.5 X. Picture also taken from large plates which has different parents combination by taking the whole of the plate and rotate the step so that each day a different plate were photographed.
Each picture of eggs was identified from numbering the stages until they hatched. We determine the approximate development stage of the eggs by using stereo microscope. For this experiment, we are using reference from Development stages of Baltic Herring Eggs from Klinkhardt, 1984 which has 17 stages for herring fish. We believed that, eggs which came from different cross will affect the developmental rate. Each glass plate that remained with eggs was being photographed by using 2 different magnifications which was 0.63X and 2.5 X. Ten eggs from each plates randomly was being identified the stages development.
Fertilization rate for eggs were observed by counting number of eggs that still alive, dead and hatched from each glass plates. The hatching was calculated based on number fertilized eggs and we compared between treatments.
After hatched, the entire bucket which contained larvae were counted and keep remained 200 larvae in each bucket while the rest were kept in the reserved tank. The larvae were offered with copepods in about 4 days. Fish larvae were checked daily so that we can see clearly fish larvae are feed or not by using stereomicroscope.
For larvae sampling, we took 12 larvae from each bucket for dry weight measurement. Meanwhile, each larvae were photographed in order to measure the length of larvae by putting them in a scale slide. Figure 2 shows that how the lengths of larvae were taken. Before taking picture, the larvae were anaesthetised by using metacaine. All the larvae we kept in oven for dry weight process. After 3 days, weight measurement was done on each larvae by using weight measurement board.
Image J analysis
For length measurement, Image J was being used in order to measure the size of larvae in millimetres length. According to Hamphey 1995, Image J is a kind of measurement technique which best on image or picture so that to avoid source of error when applying image analysis to live organisms.
For the larvae measurement, a total of 700 larvae were used. The length and weight from each 700 larvae were taken by using the same size classes which are in millimetre and grams. The statistical programmes SPSS 15 for windows were used in order to perform General Linear Model for two variables which are eggs dry weight and length of larvae between treatments.