Japanese mackerel ( Scomber japonicus ) is one of the important economic species in the pelagic light seine fishery in China, but few studies have been reported on the age, growth and management recommendations of Japanese mackerel in the high seas of the northwest Pacific Ocean. In this study, we fitted expressions for the relationship between fork length and body weight of Japanese mackerel based on fork length and body weight data of Japanese mackerel in the high seas of the Northwest Pacific Ocean from 2018 to 2019, and calculated growth parameters and growth characteristics of Japanese mackerel von Bertalanffy growth equation by identifying otolith age data combined with the least squares method. The results showed that the relationship between fork length and body weight of Japanese mackerel in the open sea of the Northwest Pacific Ocean was W = 2.0 × 10 -6 L 3.289 (r = 0.9764, n = 2833); the growth parameters were L = 447.61 ∞ , K = 0.264, t = -1.06 0 ; the growth rate reached the maximum when the bodyweight growth rate was 122 g/yr, at which the inflection point age was 3 years old, the inflection point body weight was 310 g, and the inflection point length was 309 mm. We recommend 2 years of age start fishing with a fork length of 250 mm (±10 mm). The growth parameters of Japanese mackerel in the open sea of the Northwest Pacific Ocean were not significantly different from those of the Japanese mackerel population on Japan’s coast (P > 0.05), Finally, based on the knowledge of biological research and resource evaluation, we suggest that the age of opening trap should be 2 years old and the length of fork should be 250 mm (±10 mm).
Japanese mackerel (Scomber japonicus) is an oceanic warm-water pelagic fish, one of the important economic species of China’s pelagic light seine fishery, mainly living in the northwest Pacific Ocean, divided into the Pacific group system and the Tsushima group system [
Since the Japanese mackerel fishery is of great relevance to the expansion of China’s high seas fishery and the improvement of the capacity building of the high seas fishery stock assessment system, and the strengthening of the research on the biological characteristics and stock growth of this fishery stock can provide the preliminary basic data for China’s active participation in the assessment of mackerel resources in the Northwest Pacific Fisheries Commission. In this paper, the age determination and growth characteristics of Japanese mackerel in the high seas of the Northwest Pacific Ocean from 2018 to 2019 were analyzed to provide a reference basis for resource assessment and fisheries management.
Japanese mackerel in the high seas of the Northwest Pacific Ocean, randomly collected by fishing vessels, were studied in the sampling area of 39 - 44˚N, 147 - 154˚E, and the sampling period was from April to December (fishing season) in 2018 and 2019. Samples were taken four times a month, 100 tails were taken each time, if the number of tails was less than 100, and all samples were taken totaling 2833 tails (Frozen and shipped back to the lab via transport ship). The fishing date, latitude and longitude of each sampling location were recorded, and the samples were numbered and registered. The sampling area is shown in
Body length, fork length and full length of Japanese mackerel were measured by tape measure (accurate to 1 mm); body weight was measured by electronic balance (accurate to 0.1 g, Error range in ±0.1 g). The differences between fork length and body weight of Japanese mackerel by sex were examined by analysis of covariance (ANOVA), and then the fork length-weight growth relationship was fitted by power function [
W i = a × L i b (1)
Li denotes the mean fork length (mm) of the ith fork length group, Wi is the mean weight (g) corresponding to Li, a is the condition factor for growth, and b is the power index coefficient.
During the life cycle of teleosts, the inner cavity of the skull is lined with carbonate deposits of “small stones” called otoliths. The main mineral component of otoliths is CaCO3, and fish rely on otoliths to distinguish sounds and maintain body balance [
L i R i = L R (2)
where Li is the back-calculated fork length (mm) of the ith age or annual whorl of Japanese mackerel; L is the fork length (mm) of that individual; Ri is the ith annual whorl diameter, which refers to the straight-line distance (mm) from the core point of the otolith to the ith annual whorl of the otolith, and the whorl pattern is measured by the outer edge of the opaque band; R is the otolith diameter, which refers to the straight-line distance (mm) from the core point of the otolith to the outermost edge. The schematic diagram of otolith chronology measurement is shown in
To enhance the accuracy of age identification, the otoliths used for age reading should be relatively transparent in cross-section, with the whorls clearly visible, and as much as possible, the secondary whorls should be brought together in
one place during the polishing process to reduce the interference with age identification. When measuring the diameter of the whorls on the photographs of the otoliths, the alternating zone between the transparent and opaque bands in transmitted light was used as the location of the annual whorls, and the diameter of all the secondary whorls, annual whorls and interfering whorls was recorded [
In fisheries research, the von Bertalanffy growth equation can elucidate the age-dependent variation of length and weight of fish, and the growth process can be fitted with the data of minimum parameters. The equation is generally used to fit and describe the growth pattern of fish, and the least squares method is used to determine the optimal growth parameters for the von Bertalanffy growth equation [
Fork length growth equation.
L t = L ∞ × { 1 − e [ − K × ( t − t 0 ) ] } (3)
Weight growth equation.
W t = W ∞ × { 1 − e [ − K × ( t − t 0 ) ] } (4)
Lt and Wt denote the fork length (mm) and weight value (g) of Japanese mackerel at age t; L∞ and W∞ denote the ultimate fork length (mm) and ultimate weight (g) of Japanese mackerel; t0 denotes the age when the theoretical fork length (Lt) or weight (Wt) is equal to zero, often a negative number; K is the average curvature of the growth curve, indicating the relative rate of convergence to the asymptotic value.
It was found that there was no significant difference in fork length and body weight between male and female Japanese mackerel individuals (P > 0.05). The relationship between fork length and body weight was expressed as W = 2.0 × 10−6 L3.289 (r = 0.9764,n = 2833), where the growth condition factor a was 2 × 10−6 and the power index coefficient b was 3.289 (
The total number of samples used for otolith age identification in 2018 and 2019 was 317, including 5 at age 0+, 92 at age 1+, 170 at age 2+, 44 at age 3+, and 6 at age 4+. Fork lengths and age back-calculations were performed according to the
otolith wheel diameter, and the corresponding average back-calculated fork lengths for each age were 187.83 mm at age 1+, 248.38 mm at age 2+, 294.01 mm at age 3+, and 318.46 mm at age 4+, as shown in
Based on the age and corresponding fork length data listed in
The weight growth equation is:
W t = 1046.74 × { 1 − e [ − 0.264 × ( t + 1.06 ) ] } 3.289 (5)
The weight growth rate of Japanese mackerel with age as well as weight change curve can be plotted from the weight growth equation (
Age/Fork length | L1 (mm) | L2 (mm) | L3 (mm) | L4 (mm) |
---|---|---|---|---|
1 | 187.00 | |||
2 | 185.89 | 247.85 | ||
3 | 192.64 | 251.81 | 302.72 | |
4 | 185.77 | 245.48 | 285.29 | 318.46 |
Average | 187.83 | 248.38 | 294.00 | 318.46 |
As can be seen from
The relationship between fork length and body weight of pelagic fishes has been shown to be a power function [
Most pelagic fish age identification is based on otoliths, and the resin-embedded otolith molds are polished to a thickness of about 0.2 mm by a grinding and polishing machine, and the age is identified and the whorl diameter is measured under an optical microscope, based on this age identification method it is easier to determine the actual age composition of the fish [
To verify the accuracy of otolith age identification, the growth curves of Japanese mackerel in this study were compared with those of Japanese mackerel from the Pacific group studied previously using F-test [
Comparing the results of the present study with the results of the growth equation parameters of Japanese mackerel in Japan’s coast (
Tokifusa (2017) [ | Iizuki (2002) [ | Keiichi (1966) [ | ||||
---|---|---|---|---|---|---|
F-test F-test | F-value | P-value | F-value | P-value | F-value | P-value |
In this study | 1.254 | 0.395 | 0.626 | 0.292 | 0.528 | 0.228 |
Researchers | Analysis Method | Parameter | ||
---|---|---|---|---|
L∞ (mm) | K | t0 | ||
This study (2021) | Otoliths Otolith | 447.6 | 0.2641 | −1.59 |
Tokifusa (2017) [ | Otoliths Otolith | 408.1 | 0.6 | −1.082 |
Iizuki (2002) [ | Fish Scale Scale | 411.6 | 0.49 | −0.4 |
Keiichi (1966) [ | Fish Scale Scale | 446 | 0.33 | −0.8 |
Tokifusa [
The growth rate of fish reflects how fast or slow the fish increases in length or weight throughout its life. After understanding the growth rate of fish in each life stage, the period of fast growth to slow growth can be appropriately selected and utilized to maximize the fishery resources [
This research was supported by National Key Research and Development Program of China (2019YFD0901405, 2018YFC1406802); Zhejiang ocean fishery resources exploration and capture project (CTZB-2021070657); Special Fund for Basic Scientific Research Business Expenses of the East China Sea Fisheries Research Institute of the Chinese Academy of Fisheries Sciences at the Central Level for Public Welfare (2021M06); Open Fund for the Ministry of Education/Shanghai Field Scientific Observation Research Station of the Yangtze Delta Estuarine Ecosystem (K202001); The project was completed with the support of the Open Fund of the Key Laboratory for Sustainable Development of Ocean Fishery Resources, Ministry of Education (A1-2006-00-301109). And we would not have been done without the help from many people.
National Key Research and Development Program of China (2019YFD0901405, 2018YFC1406802); Zhejiang Ocean Fishery Resources Exploration and Capture Project (CTZB-2021070657); Special Fund for Basic Scientific Research Business Expenses of the East China Sea Fisheries Research Institute of the Chinese Academy of Fisheries Sciences at the Central Level for Public Welfare (2021M06); Open Fund for the Ministry of Education/Shanghai Field Scientific Observation Research Station of the Yangtze Delta Estuarine Ecosystem (K202001).
The authors declare no conflicts of interest regarding the publication of this paper.
Zhang, H., Yang, C., Xu, B., Shi, Y.C., Zhao, G.Q. and Han, H.B. (2022) Age and Growth of Japanese Mackerel in the High Seas of the Northwest Pacific Ocean. Open Journal of Animal Sciences, 12, 91-102. https://doi.org/10.4236/ojas.2022.121007