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Article

Age and Growth of Mitre Squid (Uroteuthis chinensis) in the Northwestern South China Sea Based on Statolith Microstructure Analysis

by
Dan Liu
1,
Chi Zhang
1,
Jianzhong Guo
1,2,3,
Haozhan Wang
4,
Yumeng Pang
5 and
Yongjun Tian
1,3,*
1
Research Centre for Deep Sea and Polar Fisheries, and Key Laboratory of Mariculture, Ministry of Education, Ocean University of China, Qingdao 266100, China
2
School of Marine Science and Engineering, Qingdao Agricultural University, Qingdao 266109, China
3
Frontiers Science Center for Deep Ocean Multispheres and Earth System (FDOMES), Ocean University of China, Qingdao 266100, China
4
Sansha Marine Centre, Ministry of Natural Resources, Sansha 573199, China
5
Ocean Nexus Center, University of Washington, Seattle, WA 98195, USA
*
Author to whom correspondence should be addressed.
Diversity 2024, 16(7), 395; https://doi.org/10.3390/d16070395
Submission received: 23 May 2024 / Revised: 7 July 2024 / Accepted: 8 July 2024 / Published: 11 July 2024
(This article belongs to the Section Animal Diversity)
Browse Figures
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Abstract

:
The mitre squid Uroteuthis chinensis is distributed widely in the Chinese coastal areas and contributes to the majority of the Chinese neritic squid fishery, especially in the South China Sea. However, little has been investigated about its life history traits, despite its commercial importance. In this study, using samples of U. chinensis collected through bottom trawlers from December 2019 to March 2021 in the northwestern South China Sea, biological traits including hatching date, growth pattern and dorsal mantle length at maturity of male individuals were explored by age determination based on statolith microstructure analysis. The results indicated that the U. chinensis showed a year-round spawning pattern with three main cohorts (spring, summer and autumn) that can be identified according to their hatching season. The range of the dorsal mantle length (DML) was 117–259 mm for females and 70–312 for males, and the body weight ranged from 55.1 to 480.5 g for females and from 19.3 to 560.2 g for males; the age ranges were estimated between 82 and 173 days for females and between 76 and 175 days for males. As for the length–weight relationship, males possessed a larger mantle length than females, while the body weight of females increased more compared to males at the same mantle length. The population recruits to the fishing ground, with individuals reaching sexual maturity at around 3 months, and the lifespan is less than 200 days. The growth model is well described by the exponential equation, which revealed that spring and autumn cohorts showed a higher growth rate than summer cohorts. As for male individuals, the smallest dorsal mantle length at maturity (DML50%) was recorded in the spring cohort (DML50% = 116 mm) compared with the summer (DML50% = 129 mm) and autumn cohorts (DML50% = 149 mm). This study provides key and updated fishery biological information of U. chinensis in the South China Sea and contributes to the understanding of U. chinensis resources.

1. Introduction

World catch production by marine fisheries has maintained a high level in recent decades [1,2]. Cephalopod landings have been on the rise globally over the past decades, making up approximately 4% of global fisheries production [3], while fish stocks decrease mainly as a result of human activities and climate change. Cephalopods play a critical role in the marine ecosystem as they occupy multiple trophic levels and are not only a crucial food source for a diverse array of seabirds but also for large fish and marine mammals [4,5,6,7,8,9]. Consequently, a burgeoning interest in the study of cephalopods has emerged. Cephalopod populations are characterized by short life cycles, rapid growth, high turnover rates and strong phenotypic plasticity [10,11,12,13,14,15,16], which collectively enable them to swiftly adapt to environmental changes, thereby gaining a competitive advantage and complementing the ecological niche of other biological populations. These characteristics result in a complex population structure and great variability in the generation of biological traits [17,18]. Nonetheless, the scarcity of long-term research on age composition, size distribution and maturation present a challenge to their sustainable development and effective management.
The China Seas are an over-exploited coastal ecosystem with drastic environmental changes, which are gradually warming up with climate change [19]. Commercial fish stocks have largely declined, and individual fish tend to be small-sized due to the drastic environmental changes and over-fishing [19], while catches of coastal cephalopods in China seas have shown an increasing trend since the 1990s, especially the Loliginidae squids [20]. Eight Loliginidae squids distributed in China’s coastal waters, of which five species (Uroteuthis (Photololigo): duvaucelii, edulis and chinensis; Loliolus: beka and japonica) are commercially exploited and mainly inhabit the tropical and temperate waters [21]. However, thus far, most studies have focused on commercial ommastrephid species, such as Illex argentinus [22,23,24,25] and Dosidicus gigas [26,27,28,29,30]. As for I. argentinus, age, growth and population structure were studied; the result indicated that the life cycle was approximately one year, and two hatching groups could be identified based on the microstructure of the statolith [22]. Life history studies were conducted for only a few Loliginidae squids in the coastal China Seas [31,32], and studies of most squids, even commercially important species, is currently lacking.
The mitre squid U. chinensis, a large-sized squid with a short lifespan (less than 200 days), is mainly distributed in the warm continental shelf of the South China Sea and south-central Taiwan Strait within the 15–170 m depth range [21,31]. U. chinensis is typically harvested by various fishing methods—including jigging, trawl, light purse seine and light lift net operations—and support the largest squid fishery in the coastal waters of China accounting for about 60% of the total production of the family Loliginidae [33,34]. U. chinensis occupies a trophic level of approximately three, which plays an important role in nutrient and energy transfer by linking the upper and lower ends of the food chain [32]. Unfortunately, annual landing has dropped since 1985 in the South China Sea. A length-based Bayesian biomass study (LBB) estimated that the stock has been overfished since the mid-1980s and suggested that asymptotic length might be attributed to fishing-induced miniaturization [33]. However, the length frequency method is inappropriate for most squid species because most species live less than 1 year and the identification of discrete length–frequency modes is difficult [17]. Furthermore, the application of an inappropriate growth model could also bias the assessment result, which limits our understanding of population dynamics and hinders the management of resources [32]. As U. chinensis spawn year-round, great seasonality in the environments might lead to different environmental influences on squid biological traits throughout their life cycle. Effective fisheries management necessitates the collection of high-frequency data collection of each seasonal cohort to account for these fluctuations [17].
Currently, the hard tissues of squid are widely used in the study of life history characteristics, such as statoliths, beaks, gladii and eye lenses [4,35,36,37]. Statoliths, as the most widely used hard tissue for studying age and growth of squid, have been considered as ‘black boxes’ because of recording ecological information of the whole life history of squids [4,38]. They are located in the cartilaginous cranium of cephalopods and are paired calcareous structures composed of aragonite and calcite [38]. The daily increment of statolith has been validated in ten loliginid squid species including U. chinensis [4,39,40]. The age and growth of U. chinensis has been studied during the past decades. Jin conducted a comparative analysis age and growth of U. chinensis and U. edulis collected in the East China Sea and South China Sea but without sampling for an entire year, so characteristics of the population structure still remain unclear [31]. Liao collected sufficient samples to analyze, comparing samples from different regions separately along the Taiwan Strait [32]. To our best knowledge, there is a scarcity of studies on the biological traits and population structure of U. chinensis in the South China Sea.
Therefore, in this study, samples of U. chinensis from December 2019 to March 2021 along the southern continental shelf of the Hainan Island in the South China Sea were collected. Through meticulous analysis of statolith microstructures, the daily age and discerned seasonal cohorts of U. chinensis were accurately determined. Biological characteristics of U. chinensis, including their length–weight relationship, growth and male maturation size, were applied to identify seasonal and sexual variations in U. chinensis. This multifaceted evaluation provided a robust framework for assessing the biological characteristics.

2. Materials and Methods

2.1. Sample Collection

Squids were collected from December 2019 to March 2021 off the southern coast of Hainan Island (Figure 1, Table 1). To minimize selectivity of fish gear, samples were collected from a commercial bottom trawler to ensure a representative size range. All of these samples were frozen (−20 °C) and transported to the laboratory for lab examinations. U. chinensis was identified according to the anatomical characteristics of the tentacles’ and arms’ sucker rings [41]. Dorsal mantle length (DML, 1 mm) and weight (0.1 g) were measured for each individual. The gonadal development stage was visually assessed based on the Lipinski and Underhill method (i.e., I and II, immature; III, maturing; IV and V, mature; VI, spent) [42,43,44]. A pair of statoliths of each sample were extracted, cleaned with ultrasonic cleaner and stored in microtubes after drying.

2.2. Statoliths Processing and Reading

The shape and position of statoliths in loliginids does not differ significantly between males and females, and morphological parameters of left and right statoliths are very similar in microstructural appearance [30,40,45]; therefore, one statolith from each pair was randomly embedded in epoxy resin (Buehler, Epothin, Lake Bluff, IL, USA) and grounded with alternating fine waterproof sandpapers (Buehler, 600 to 4000 grits) from the anterior concave side until full exposure of focus and then polished with 0.3 μm aluminum powder [46]. The growth rings can be seen clearly and are composed of a pair of dark ring and light ring (Figure 2). The polished statoliths were photographed under an optical microscope (200× magnification) using a microscope system (OLYMPUS BX53 and DP74). For each statolith, the total number of increments was counted from the hatch ring to the tip of the rostrum [38,47]. Age was determined as the total number of dark rings, since that statolith increment deposition of U. chinensis was suggested to have a daily rhythm [48]. To improve the ageing precision, the number of increments were counted three times by one reader at an interval of a month. When the increment counts differed by less than 10%, the three counts were averaged to determine the daily age with enhanced accuracy. The individuals that differed by more than 10% were excluded from subsequent analysis. Hatch date for each individual was back-calculated by subtracting daily age from the day of capture, and the hatching cohort was also assigned. Sample number for each month was standardized to calculate hatching frequency.

2.3. Data Analysis

The length–weight relationship (LWR) was fitted with the least squares method for sexes and identified male cohorts separately [32]. The relationship is expressed as the following power model:
W = aLb
where W is weight (g), L is DML (mm), a is intercept representing the average condition factor and b is slope as allometric growth coefficient. The effect of sex and cohort on exponent b of the length–weight relationships was investigated using a test for homogeneity of slopes (ANCOVA).
Since U. chinensis maintains a high growth rate across its whole life, the exponential equation was applied to the relationship between the estimated age (days) and DML (mm) as Liao [32] suggested. The equation was expressed as
Lt = aebt
where t is age (day); Lt is DML at age t; and a and b are the model parameters to be estimated. The growth differences between sexes and among cohorts were also compared with ANCOVA test.
Immature/maturing male individuals were classified as “0” and mature ones as “1”, and DML was treated as covariate. Then, the logistic regression model was fitted to estimate the DML at first maturation (DML50%) among various cohorts as the following:
Pi = 1/(1 + e−b(Li−DML50%))
where Pi is the relative frequency of sexually mature individuals in DML class Li; b is regression parameters. In addition, maturity range (MR25%–75%) is calculated. Differences in size at maturity among cohorts were analyzed by one-way ANOVA.
Due to the limited sample size of females, only male individuals were analyzed separately by cohorts (see Results). All statistical analyses were conducted using R 3.6.1 [49,50].

3. Results

3.1. Dorsal Mantle Length, Weight and Age Distributions

A total of 512 individuals (92.1% of total samples) were precisely aged (Table 1). DML ranged from 70–312 mm with a unimodal distribution, and individuals with DML over 200 mm were mostly collected in summer, autumn and winter (Table 1). Weights ranged from 19.3 to 560.2 g and were mainly concentrated between 50 and 150 g, accounting of 65.6% (Table 1).
DML for females ranged from 117 to 259 mm, of which 85.06% were 120–210 mm individuals, and from 70 to 312 mm for males. As for weight, females ranged from 55.1 to 480.5 g, with two peaks, and males ranged from 19.3 to 560.2 g, concentrated between 50 and 150 g (Figure 3, Table 1).
The maximum age is 175 days for a male individual. The estimated daily age was 82–173 days and 76–175 days for females and males, respectively. Three cohorts were identified according to the frequency distribution of hatching dates, namely, the spring cohort from March to May, summer cohort from July to September and autumn cohort from October to December, of which the spring and summer cohorts are the dominant hatching seasons for U. chinensis samples (Figure 4; Table 2).
Overall, DML ranged from 70 to 229 mm for the spring cohort, 94 to 312 mm for the summer cohort and 100 to 297 mm for the autumn cohort. Weight ranged from 19.3 to 291.8 g, 29.9 to 560.2 g and 40.8 to 410.9 g for the spring, summer and autumn cohorts separately. Besides, age ranged from 88 to 159 days for the spring cohort, 76 to 175 days for the summer cohort and 82 to 173 days for the autumn cohort (Table 2). The summer cohort occupies the largest proportion of the whole samples.

3.2. Length–Weight Relationship

The length–weight relationship for U. chinensis was estimated as follows (Figure 5):
Female: W = 0.0004L2.4942 (n = 87, R2 = 0.907);
Male: W = 0.0011L2.2843 (n = 425, R2 = 0.923);
Male—Spring: W = 0.0005L2.4195 (n = 82, R2 = 0.959);
Male—Summer: W = 0.0008L2.3367 (n = 252, R2 = 0.889);
Male—Autumn: W = 0.0025L2.1168 (n = 80, R2 = 0.955).
The b value of each equation was lower than 3, indicating that the growth of U. chinensis is negative allometric. A significant difference was detected between sexes (p-value = 0.0217), and the weight of females increased faster with increased DML. For male cohorts, a significant difference was detected between spring and autumn (p-value < 0.001) and between summer and autumn (p-value = 0.0067).

3.3. Growth Model

The growth model was described by an exponential model as follows (Figure 6):
Female: L = 76.674e0.0068t;
Male: L = 52.651e0.0092t;
Male—Spring: L = 43.317e0.01t;
Male—Summer: L = 55.83e0.0086t;
Male—Autumn: L = 46.566e0.011t.
Males showed significantly a higher growth rate than females (p-value = 0.0309), and the growth curves crossed around 150 mm of dorsal mantle length. For male cohorts, a significant difference was detected between spring and summer (p-value = 0.0316) and between summer and autumn (p-value = 0.0469), and the lowest growth rate was recorded in summer.

3.4. DML at First Maturation

There were 49 mature females, with the remaining females in the process of maturing, of which the proportion of maturing females were lowest in the spring cohort and highest in the summer cohort. The proportion of mature male individuals reached more than 50% in each cohort and even 74.2% in summer (Table 3). The minimum dorsal mantle length of mature males gradually increased in the order of spring, summer and autumn.
The equations were fitted as the following (Figure 7):
Male—Spring: Pi = 1/(1 + e−0.08512(Li−116.4));
Male—Summer: Pi = 1/(1 + e−0.1413(Li−128.6));
Male—Autumn: Pi = 1/(1 + e−0.0956(Li−149.4)).
In the male population, DML50% was 116 mm for the spring cohort, 129 mm for the summer cohort and 149 mm for the autumn cohort. The spring and summer cohorts showed smaller DML50% compared to the autumn cohort (p-value < 0.001).

4. Discussion

In this study, the proportion of male and female individuals varied dramatically due to having very few females, with only 10 samples in the autumn cohort. The current studies of U. chinensis have not shown significance in the differences in the numbers of males and females [40,51,52,53,54]. Some studies simply stated the number of male and female samples but did not focus on the differences between their numbers. Liao collected 4099 samples of U. chinensis in the Taiwan Strait, but the result showed that female numbers (1685 samples) are still less than that of males (2328 samples) [32]. Jin used 174 samples of U. chinensis, of which the number of female individuals was only 72 [31]. These studies all relied on samples obtained through commercial fishing, which showed fewer female samples. Therefore, the cause of this difference may be related to biases in the sampling process. In general, females are plumper and of good quality when they reach sexual maturity and are of high commercial value; so, they may be preferentially selected by fishermen prior to sampling, potentially skewing the sample composition before it reaches the research stage. Subsequent sampling methodologies must also be designed to mitigate this issue as much as possible to further ensure that the collected samples maintain the necessary quantity, quality and demographic proportion. Furthermore, the situation may also be related to differences in their respective habitats, reproductive strategies and especially sea surface temperature [55]. It has been shown that temperature changes generally do not lead to changes in sperm activity in cephalopod males but can affect the number and size of eggs laid by females to a certain extent, which potentially results in a more pronounced difference in the population numbers of males and females. In addition, a similar situation appeared in Loligo reynaudii in 1988, where males outnumbered females in 11 of the 15 months investigated because of the differences in the spawning and mating behavior between the two sexes and the features of the general three-dimensional layout and zones of activity on a typical spawning arena [5,44]. Therefore, future studies need to consider reproductive methods of U. chinensis and compare them with L. reynaudii.
A significant difference in the dorsal mantle length–weight relationship was detected between sexes for U. chinensis in the South China Sea. Similar reports of sexual dimorphism were also reported for the U. chinensis population in the Taiwan Strait [32] and Andaman Sea [34]. The daily age through statolith microstructure analysis provided further insight into the growth patterns of U. chinensis. The maximum age estimated in this study was 175 days, aligning with the trait as a short lifespan, indicating a probable lifespan of approximately 6 months for U. chinensis, similar to the age observed in the Taiwan Strait [32]. In addition, the minimum age estimated was 76 days, namely, individuals recruited to a fishery at an age of less than 3 months. The back-calculated hatch time further corroborates the year-round spawning activity of U. chinensis and spawning seasons mainly concentrated from March to May and July to September. These results were consistent with the result of Dong [41] but different to the result of Liao [32] in the Taiwan Strait. The hatching months of U. chinensis in Liao’s study are mainly concentrated from January to April [32]. Furthermore, a significant regional difference in spawning time was also reported in the Taiwan Strait between the north and south populations, which warrants further investigation.
The growth model displayed that males grow significantly faster than females and to a larger size for U. chinensis, a finding that is consistent with previous results [32,56,57]. The result could be attributed to the different spawning strategies, since males need to compete with each other for mating opportunities [57] and tend to allocate less energy into reproduction but more input for faster size growing [40]; this is in contrast to females that need to store more energy for reproduction, which appears as increasing weight.
Considering the growth model and the smallest dorsal mantle length at maturity together, the minimum maturing age was around 3 months old in this study. Thus, combined with life span, the spring cohort could spawn from July to October, the summer cohort from October to January of the next year and the autumn cohort in the spring of the next year. Such cohort alternation is a common strategy for squids to adapt to the quickly changing conditions of oceanographic environments. Similar patterns were also recorded in U. edulis [58], Sepioteuthis lessoniana [59] and Illex coindetii [60]. The alternation also resulted in temporal overlap of different cohorts in the same season, especially during summer and autumn.
A number of studies revealed seasonal variations in the growth of squids [61,62]. An increase in water temperature could dramatically affect growth rate, known as Forsythe’s hypothesis, and cohorts hatched in warm seasons might demonstrate a faster growth rate and shorter lifespan [63,64]. Consistent with Forsythe’s hypothesis, a higher growth rate was recorded in the spring cohort that experienced warm temperatures during spring and summer for U. chinensis. By contrast, the autumn cohort that experienced lower temperature in autumn and winter also showed a higher growth rate. The result is also related to food availability. Yan et al. [52] reported significant seasonal variation in trophic level, higher in winter and spring and lower in summer and autumn, of U. chinensis in the ecosystem of the south China Sea. The report suggests that prey abundance and availability can fluctuate markedly with seasons. Thus, the autumn cohort may experience better prey availability and also show a higher weight increase. As for maturity, body size highlights that threshold and temperature could exert a decisive influence after an individual reaches the minimum size of maturity [65]. Consistently, the spring cohort first matured at the smallest DML, the autumn cohort with comparable growth rate matured later and the medium value was recorded in the summer cohort that experienced warm temperature and showed a slower growth rate. Spring cohorts experience progressively warmer water temperatures as they grow, while individuals hatched in summer and autumn encounter progressively cooler water temperatures over time [64,65]. Consequently, the smallest dorsal mantle length at maturity appears to increase progressively with each season. However, the data showing the experience of U. chinensis in environmental and water temperatures need to be supplemented and will need to be revisited in the future.

5. Conclusions

This study provides population structure and biological characteristics on the life history of U. chinensis in the northwestern South China Sea. The management of cephalopod populations poses a complex challenge, largely due to their complicated life history traits. Considerable seasonal variations further support the flexibility and plasticity of biological traits of U. chinensis. These findings provide valuable insight into the growth patterns and contribute to the understanding of cephalopod resources. Further research endeavors could beneficially focus on the interplay between environmental factors and biological information.

Author Contributions

Methodology, C.Z.; formal analysis, D.L. and J.G.; resources, H.W.; data curation, D.L. and J.G.; writing—original draft preparation, D.L.; writing—review and editing, C.Z. and Y.P.; visualization, D.L.; funding acquisition, Y.T. All authors have read and agreed to the published version of the manuscript.

Funding

This work was partially supported by the National Natural Science Foundation of China (Nos. 42376100 and 41930534), and the Taishan Scholar Foundation of Shandong Province (tsqn202211052).

Institutional Review Board Statement

Ethical review and approval were waived for this study due to the following reason: our research subject is a commercial species in the South China Sea, and the samples used in this study are from commercial fisheries that do not raise any animal ethics issues. The process of torturing animals to painful death didn’t exist.

Data Availability Statement

The data presented in this study are available on request from the corresponding author.

Conflicts of Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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Figure 1. Sample area (shaded area) of Uroteuthis chinensis in the northwestern South China Sea.
Figure 1. Sample area (shaded area) of Uroteuthis chinensis in the northwestern South China Sea.
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Figure 2. A polished statolith of Uroteuthis chinensis showing the ageing axis (hatch ring to rostrum) from a male individual (DML: 100 mm; Age: 110 days).
Figure 2. A polished statolith of Uroteuthis chinensis showing the ageing axis (hatch ring to rostrum) from a male individual (DML: 100 mm; Age: 110 days).
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Figure 3. Number of sample individuals for dorsal mantle length and weight.
Figure 3. Number of sample individuals for dorsal mantle length and weight.
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Figure 4. Number of individuals that hatched per month for males and females.
Figure 4. Number of individuals that hatched per month for males and females.
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Figure 5. Power model fitted to the relationship between dorsal mantle length and weight by sexes (a); male cohorts of Uroteuthis chinensis (b).
Figure 5. Power model fitted to the relationship between dorsal mantle length and weight by sexes (a); male cohorts of Uroteuthis chinensis (b).
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Figure 6. Exponential growth model of Uroteuthis chinensis fitted to dorsal mantle length and daily age by sexes (a); male cohorts (b).
Figure 6. Exponential growth model of Uroteuthis chinensis fitted to dorsal mantle length and daily age by sexes (a); male cohorts (b).
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Figure 7. Logistic regression curves to the maturity-proportion-at-age data for male Uroteuthis chinensis of the three seasonal cohorts (Maturity Range: MR25%–75%).
Figure 7. Logistic regression curves to the maturity-proportion-at-age data for male Uroteuthis chinensis of the three seasonal cohorts (Maturity Range: MR25%–75%).
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Table 1. Sample information of Uroteuthis chinensis used for life history characteristics analysis.
Table 1. Sample information of Uroteuthis chinensis used for life history characteristics analysis.
YearMonthNumber of IndividualsDML Range (mm)Weight Range (g)
FMF (Mean)M (Mean)F (Mean)M (Mean)
2019
December2323125–168
(141)		113–183
(139)		55.1–117.4
(80.9)		44.0–136.0
(73.7)
2020
January1335135–192
(165)		122–195
(158)		90.7–188.4
(134.9)		55.4–151.1
(103.0)
April841194–259
(214)		179–297
(213)		180.3–360.2
(242.5)		148.3–410.9
(221.4)
July15912670–170
(126)		82.319.3–166.7
(71.0)
September2423169–215
(191)		151–229
(177)		150.0–279.3
(200.5)		118.8–291.8
(158.6)
November287182–190
(186)		94–218
(140)		181.2–198.2
(189.7)		29.9–203.9
(94.6)
December366140–176
(153)		137–173
(155)		105.5–140.2
(121.7)		81.2–163.0
(115.4)
2021
January1269117–253
(197)		110–312
(159)		62.0–480.5
(259.2)		49.2–560.2
(141.2)
March122125100–144
(121)		95.840.8–93.9
(67.1)
Table 2. Sample information of Uroteuthis chinensis of the three seasonal cohorts.
Table 2. Sample information of Uroteuthis chinensis of the three seasonal cohorts.
CohortNumberDML Range (mm)Weight Range (g)Age Range (Days)
FMF (Mean)M (Mean)F (Mean)M (Mean)F (Mean)M (Mean)
Spring2582126–215
(188)		70–229
(140)		82.3–279.3
(195.8)		19.3–291.8
(95.6)		107–159
(132)		88–159
(116)
Summer50252117–253
(113)		94–312
(151)		55.1–480.5
(141.7)		29.9–560.2
(112.5)		85–154
(113)		76–175
(115)
Autumn1180125–259
(192)		100–297
(165)		69.5–360.2
(202.2)		40.8–410.9
(136.3)		82–173
(122)		85–161
(113)
Table 3. Mature sample information of the three seasonal cohorts of Uroteuthis chinensis.
Table 3. Mature sample information of the three seasonal cohorts of Uroteuthis chinensis.
CohortNumber of Mature IndividualsDML Range (mm)Age Range (Days)
FMFMFM
Spring1758169–215
(193 ± 14)		90–229
(157 ± 32)		107–159
(126 ± 14)		88–159
(120 ± 14)
Summer25187132–253
(182 ± 28)		108–312
(162 ± 35)		90–154
(120 ± 15)		76–175
(116 ± 15)
Autumn744125–235
(198 ± 27)		122–297
(198 ± 31)		94–138
(126 ± 15)		86–161
(122 ± 15)
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Liu, D.; Zhang, C.; Guo, J.; Wang, H.; Pang, Y.; Tian, Y. Age and Growth of Mitre Squid (Uroteuthis chinensis) in the Northwestern South China Sea Based on Statolith Microstructure Analysis. Diversity 2024, 16, 395. https://doi.org/10.3390/d16070395

AMA Style

Liu D, Zhang C, Guo J, Wang H, Pang Y, Tian Y. Age and Growth of Mitre Squid (Uroteuthis chinensis) in the Northwestern South China Sea Based on Statolith Microstructure Analysis. Diversity. 2024; 16(7):395. https://doi.org/10.3390/d16070395

Chicago/Turabian Style

Liu, Dan, Chi Zhang, Jianzhong Guo, Haozhan Wang, Yumeng Pang, and Yongjun Tian. 2024. "Age and Growth of Mitre Squid (Uroteuthis chinensis) in the Northwestern South China Sea Based on Statolith Microstructure Analysis" Diversity 16, no. 7: 395. https://doi.org/10.3390/d16070395

APA Style

Liu, D., Zhang, C., Guo, J., Wang, H., Pang, Y., & Tian, Y. (2024). Age and Growth of Mitre Squid (Uroteuthis chinensis) in the Northwestern South China Sea Based on Statolith Microstructure Analysis. Diversity, 16(7), 395. https://doi.org/10.3390/d16070395

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