Impact of Seasonal Variation on the Growth Dynamics of the Marine Catfish, Arius maculatus (Siluriformes: Ariidae) Collected from Karachi Fish Harbour
Muhammad Amin1*, Mohammad Shoaib1, Naveed Ahmad2, Mohammad Attaullah3, Ayaz Ali Khan4, Hazrat Ali5, Masarrat Yousuf1, Felipe Morcillo6, Ivar Zekker7,
Islam Dad Buneri1 and Mohamad Nor Azra8
1Department of Zoology, University of Karachi, Karachi, Pakistan
2Aquatic Diagnostic and Research Center Bahria University, Karachi-75260, Pakistan
3Department of Zoology, University of Malakand, Chakdara, Lower Dir, Khyber Pakhtunkhwa, Pakistan
4Department of Biotechnology, University of Malakand, Chakdara, Lower Dir, Khyber Pakhtunkhwa, Pakistan
5Department of Chemistry, University of Malakand, Chakdara, Lower Dir, Khyber Pakhtunkhwa, Pakistan
6Department of Biodiversity, Ecology and Evolution, Faculty of Biological Sciences, Complutense University of Madrid E-28040 Madrid, Spain
7Institute of Chemistry, University of Tartu, 14a Ravila St., Tartu, Estonia
8Institute of Tropical Aquaculture and Fisheries, Universiti Malaysia Terengganu, Kuala Nerus, Terengganu, Malaysia
ABSTRACT
Overfishing is the main cause of fish stock exploitation in the marine environment. In the current study growth dynamics of the marine catfish, Arius maculatus collected from Karachi Fish Harbour were studied. The relationship between total length and weight (W=aLb) was significantly linear (p<0.001). The condition factor (Kf) varied from 1.06±0.12to 1.23±0.07. The ‘b’ values and R2 values indicated that the growth was significantly (p<0.001) positive allometric (b>3) in the monsoons season while in the pre- and post-monsoon the growth was reported as significantly negative allometric (b<3). The negative allometric growth shows that the fish are unable to maintain their shape in the specific season. It is suggested to stop the fishing activities for marine catfishes during the spawning and oral incubation period in pre-monsoon especially from February to mid-April to ensure sustainable fishing with a better growth dynamic.
Article Information
Received 25 November 2023
Revised 05 January 2024
Accepted 24 January 2024
Available online 23 April 2024
(early access)
Published 09 June 2025
Authors’ Contribution
MA conceived the idea and wrote the
manuscript. NA helped in experimental work. MA assisted in data analysis. AAK and HA evaluated the statistical data. MA revised the manuscript. FM and IZ reviewed and improved the manuscript, IDB and MNA helped in literature search, MS, supervised the work.
Key words
Arius maculatus, Growth dynamics, Marine catfish, Length-weight relationship, Condition factor, Spotted catfish
DOI: https://dx.doi.org/10.17582/journal.pjz/20231125071011
* Corresponding author: [email protected]
0030-9923/2025/0004-1641 $ 9.00/00
Copyright 2025 by the authors. Licensee Zoological Society of Pakistan.
This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
INTRODUCTION
Catfishes of the family Ariidae, vulnerable to overfishing have a long life, delayed maturation, single spawning season, low fecundity and oral incubation (Rimmer and Merrick, 1982; King and McFarlane, 2003; Winemiller, 2005). Especially these catfishes are vulnerable to overfishing (King and McFarlane, 2003; Winemiller, 2005). Catfish utilize a huge diversity of both plant and animal protein, and can adapt to unfavorable ecological conditions. Marine catfish tolerate a wide range of salinities between open sea and fresh water. They have soft scale less bodies, are greatly appreciated by consumers and maintain a healthy condition in both fresh and dried conditions (Amin et al., 2016).
Growth dynamics in fish populations could be calculated by length-weight relationship (LWR) parameters (Morato et al., 2001). According to Beyer (1987), LWR helps to understand a mathematical relation between the two variables of length and weight. The growth dynamic relationship is different among species because of their body shape and within species due to the condition of individual fish (Schneider et al., 2000). The condition factor is used to compare the condition, fatness or wellbeing of fish (Ahmed et al., 2011). LWR is an important tool for stock assessment, growth dynamic studies in fish population and for condition factor estimation (Abdurahiman et al., 2004; Dutta et al., 2012; Eagderi et al., 2020). Overfishing is among the major threats to fish depletion as the landing doubled in the last two decades, mostly due to the demands of alien fisheries (Dulvy et al., 2003; FAO, 2020a). Besides the financial worth of fisheries for numerous countries, fish is the dominant source of protein for human populations (FAO, 2020a). Relative body condition is an important indicator of the growth and reproduction of individuals or population (Gubiani et al., 2020; Jakob et al., 1996). Fish LWR parameters are important indicators for differentiation of taxonomic units and the changes in various progressive events such as metamorphosis, growth and maturity commencement (Mims and Knaub, 1993; Thomas et al., 2003; Alvarez- Lajonchère, 2012). It also increases the knowledge regarding commercially important fish natural history. Thus, making conservation possible as well as giving clues on climatic change impact in fisheries (Sarkar et al., 2013). The condition factor (K), is used to determine existing and upcoming population success by its influence on survival, growth and reproduction (Le Cren, 1951). Fulton’s condition factor (Kf) is commonly used in the investigation of ontogenetic changes (Safran, 1992) and for life-history comparisons (Petrakis and Stergiou, 1995; Simon et al., 2009). Different values in Kf of a fish reveal the condition of sexual maturity, the level of food source accessibility, age, gender of various species (Anibeze, 2000). These relationships are also a necessary component of Fish Base (Froese and Pauly, 2012). The relative condition factor (Kn) introduced by le Cren (1951) balances for alterations in form or condition with length and could be applied to show whether an individual is in a better (Kn>1) or bad (Kn<1) state than a standard individual of the equal length.
The earlier studies on Arius maculatus, also known as spotted catfish, were mainly on the growth and food habitat (Mazlan et al., 2008). The current study aims to investigate the effects of seasonal variation on the growth dynamic of commercially important marine catfish A. maculatus. This study could help in sustainable fisheries management and provides the baseline for future study within the Arabian Sea.
MATERIALS AND METHODS
Study area
The chief fish harbor of Pakistan is Karachi Fish Harbour, which controls about 90% of fish and seafood catch in Pakistan (Pakissan.com, 2001-2007). The fishes samples were collected from Karachi Fish Harbour, West Wharf Karachi coast which is located at 66o 8/E longitude and 24o48/N latitude on the northeastern borderline of the Arabian Sea. Karachi has a temperate climate. The annual average temperature and rainfall are 21.15-30.78°C and 209.44mm, respectively. According to the Economic Survey of Pakistan, fisheries are the major source of livelihoods for many countryside communities inhabiting the coastline of Sindh and Baluchistan. Fish catch has decreased over the past two decades leading to poor socio-economy in the coastal areas of Pakistan. The Pakistan fish industry fetched 5.6 billion Rs in 2009-2010 and also employs 1 percent of the country’s population and generates 1.3% of Pakistan’s GDP (GOP, 2010).
Collection of material
Arius maculatus was seasonally (pre-monsoon, monsoon and post-monsoon) collected from Karachi Fish Harbour on weekly basis. Bottom trawls were used for catching the fishes off the shore and gill net was used to catch the fish in the coastal area in Arabian Sea. Specimens were identified with the assistance of FAO (Fischer and Whitehead, 1974) and Bianchi (1985) guidelines.
Length- weight relationship
Fish were sexed as male and female by observing the gonads. For each individual, total length (TL) was calculated from the lower jaw tip to the end of the caudal fin to the nearest 0.1 cm using a steel scale and whole-body weight (BW) was taken on a digital balance (Hytek) with 0.1 g accuracy. LWR were calculated by the formula of linear regression using Equation 1:
The LWR was estimated using the Equation 2:
Where W is the derived weight, TL is total length (mm), a is the regression intercept curve and b is the regression coefficient. The length-weight relationship between males and females were calculated separately. When ‘b’ value is equal to 3 (b=3), the growth is isometric while the higher (b>3) and lower (b<3) values than 3 are called positive and negative allometric, respectively. The values of a and b were calculated by Equation 3. Student’s t-test was applied to confirm the difference in significance of the isometric (b=3) b values.
Condition factor (Kf) and relative condition factor (Kn)
Condition factor (Kf) and relative condition factor (Kn) of the fish were calculated by the Equations 4 and 5, respectively:
Kf= 100× W/L3 (Fulton, 1904) …(4)
Kn= W/aLb (Le Cren, 1951) …(5)
The values of a and b are taken from the logarithmic LWR equation.
Excel 2007 was used for data analysis and statistics. A p-value< 0.05 was considered significant.
RESULTS
During the study period, 204 male and 141 female of A. maculatus were collected. The highest number of the specimens were recorded in order monsoon (160) > post-monsoon (97) > pre-monsoon (88). In males the mean total length and weight were recorded as 40.23 ±0.39cm in monsoon and 37±0.23 cm in pre-monsoon and 794.9±18.2 g in monsoon and 566.6±4.6 g in pre-monsoon, respectively. In female the maximum total length (41±0.41 cm) and weight (807.12±14.55 g) were obtained in monsoon and post-monsoon season, respectively. The lowest mean total length (33.55±0.504 cm) and weight (596±16 g) were measured in pre-monsoon (Table I).
The overall allometric coefficient b for LWR in the entire three seasons for combined sexes (Fig. 1) indicated negative allometric growth (b<3) and coefficient of determination (R2) was reported as significant (<0.5) (LogW =-0.709+2.23TL, r2 = 0.701). Fulton condition factor (Kf = 100×W/L3) for overall data was 2.310. The highest (1.2) and the lowest (1.06) Kf (Kf = 100×W/L3) were recorded during monsoon in male and female, respectively (Fig. 2).
The growth of male specimens in pre-monsoon was negatively allometric (W = 1.04×TL1.08and R2 = 0.902). The Student’s t-test indicated a highly significant changes as the slope is different from the slope of 3 (t= - 241.12**, p<0.001) (Fig. 3A, Table II). The growth of female specimens in pre-monsoon was also negatively allometric (W = 0.50×TL2.07and R2 = 0.834). The Student’s t test indicated a highly significant changes as the slope is different from the theoretical slope of 3 (t= 78.40**, p<0.001) (Fig. 3B, Table II).
The growth of A. maculatus male in monsoon was positive allometric as its ‘b’ value was found to be 3.22 and the LWR was W = 2.35× TL3.22 (Fig. 4A, Table II). The R2 value was 0.329. The Student’s t test (102** p<0.001) indicated a highly significant change in LWR. The growth of female in monsoon was reported as negatively allometric (W = 0.5×TL2.1 and R2 = 0.853) with a highly significance in-test (75.88**, p<0.001) (Fig. 4B, Table II). The growth of A. maculatus male in post-monsoon was W= 1.13×TL2.25 and R2= 0.754 (Fig. 5A) where the ‘b’ value was 2.945, the R2 value was 0.9923 so the growth indicated
Table I. Seasonal variation in growth indices of male and female marine catfish, A. maculatus.
|
Pre-Monsoon |
Monsoon |
Post-Monsoon |
||||||||||
|
Male (n=48) |
Female (n=40) |
Male (n=90) |
Female (n=70) |
Male (n=66) |
Female (n=31) |
|||||||
|
TL (cm) |
W (g) |
TL (cm) |
W (g) |
TL (cm) |
W (g) |
TL (cm) |
W (g) |
TL (cm) |
W (g) |
TL (cm) |
W (g) |
|
|
Min-Max. |
34-42 |
495-615 |
31.5-42 |
378-716 |
34-45.65 |
512-1133 |
34-47 |
492-1016 |
33-46 |
576-1082 |
37-45 |
695-960 |
|
Mean±S.E. |
37± 0.23 |
566.6± 4.65 |
33.8± 0.504 |
596.8± 16 |
40.2± 0.39 |
794.9± 18.23 |
41± 0.41 |
741.7± 17.55 |
39.2± 0.32 |
774.6± 20 |
40.8± 0.55 |
801.75± 14.55 |
N, sample size; TL, total length; W, weight; g, gram; Min, minimum; Max, maximum; S.E., standard error.
Table II. Length-Weight relationships (log10 transformed) of male and female marine catfish A. maculatus.
|
Equation W=a + b × TL |
Pre-Monsoon |
Monsoon |
Post-Monsoon |
|||
|
Male |
Female |
Male |
Female |
Male |
Female |
|
|
a |
1.04 |
-0.50 |
2.34 |
0.56 |
1.12 |
5.45 |
|
S.E. (a) |
0.23 |
0.236 |
0.95 |
0.24 |
0.39 |
0.32 |
|
b |
1.08 |
2.07 |
3.23 |
2.12 |
2.55 |
1.55 |
|
S.E. (b) |
0.146 |
0.15 |
0.58 |
0.25 |
0.24 |
0.20 |
|
R2 |
0.555 |
0.834 |
0.32 |
0.857 |
0.75 |
0.74 |
|
Mean Kf ± S.E. |
1.124±0.5 |
1.12±0.02 |
1.2±.02 |
1.06±0.12 |
1.2±0.03 |
1.2±0.07 |
|
Mean Kn ± S.E. |
00 |
0.833±0.01 |
00 |
0.6±0.01 |
0.06±0.001 |
0.59±0.02 |
|
t-test |
-241.1** |
78.40** |
102** |
75.8** |
81.8** |
105.1** |
|
p-value |
0.001 |
0.001 |
0.001 |
0.001 |
0.001 |
0.001 |
a, intercept; b, slope; R2, coefficient of determination; **, highly significant; Kf, represent Fulton; Kn, relative condition factors; p<0.05 significant; p<0.001 highly significant.
negative allometric. The t test was found highly significant as 81.88** where p<0.001 (Table II). In post-monsoon season the growth in female specimens was noted as negatively allometric (W= 5.44×TL1.55and R2 = 0.787) with a highly significant t-test (105.12**, p<0.001) (Fig. 5B, Table II). The relative condition factor (Kn) was recorded in females only where the highest value was recorded in pre-monsoon (0.833±0.01) followed by monsoon (0.6±0.01) and then post-monsoon (0.59±0.02) (Table II).
DISCUSSION
The current results indicated a linear relationship of increase in weight with length, however, this ratio shows variation in various fish species, habitat, health condition, water temperature and food (Le Cren, 1951; Hossain and Ohtomi, 2010). The b value was used in the length-weight relationship (LWR) as the indicator of growth. The value of LWR (b) close to 3 indicates isometric growth, but its higher (b>3) and lower (b<3) values than 3 indicate positive and negative allometric growth, respectively (Tesch et al., 1971). In the current study, the highest and lowest significant (p<0.001) b values were reported during monsoon and pre-monsoon in male, respectively. The combined overall b value in the entire season was also reported as negative allomeric (2.32). Similar results where b value is 1 (pre-monsoon, 1.79; monsoon, 1.07; post-monsoon, 1.13; overall, 1.11) were also reported by Muzaffar et al. (2020) in Rastrelliger kanagurta. Chu et al. (2012) reported in A. maculatus, a significant highest b value (b=3.04) in monsoon and the lowest (b=2.83) in post-monsoon. Our findings also support the study of Chu et al. (2012). The b values of the different catfish species, Arius gagora, Neutoma caelatus, A. tenuispinis, Osteogeneiosus militaris had shown positive allometry and Neutoma bilineata, A. dussumieri and Neutoma thalassina were indicating negative allometry. The b values above isometric (b=3) of large specimens are the result of increase in girth (Froese, 2006). The b values for A. dussumieri and Arius caelatus reported by Dutta and Hazra (2013) and from West Bengal Froese (2006) were close to the current findings of A. maculatus. The allometric growth in b values depend on several factors such as sex, gonad maturity, physiology, season, habitat, food, stomach fullness, length frequency and fishing gear (Tesch, 1968; Gayanilo and Pauly, 1997; De Giosa et al., 2014; Eduardo et al., 2019, 2020a; Grimaldo et al., 2020; Slayden, 2020; López-Pérezet al., 2020). Thus, the negative and positive allometric growth in fishes indicate poor habitat conditions and optimum habitat conditions, respectively (Abowei, 2010).
In this study the coefficient of determination (R2) is between 0.32 (male) to 0.859 (female) in monsoon. The high R2 (r2 >0.5) values indicate good growth rate and less than 0.5 shows growth rate is abnormal (Afsarullah et al., 2015).
Kf indicates the plumpness, maturity and spawning gonadal development and general fitness of the fish (Wootton, 1990). Condition factor of A. maculatus in the current study is between 1.23±.02 (male) to 1.06±0 (female) in monsoon season. However, the Kf factor of fish can be affected by some factors such as stress, gender, season, nutrition and other ecological parameters (Khallaf et al., 2003).
Relative condition factor (Kn) of the current study indicated that the highest Kn value was reported in pre-monsoon (0.833±0.01) and the lowest in post-monsoon (0.59±0.02) (Table II). Higher Kn values indicate that the fish in good condition. Vazzoler (1996) reported that the lowest K values during the mature gonad stages indicated that the resource had been transferred to the gonads during the reproduction cycle. The present maximum Kn value in pre-monsoon indicated contradiction with reports of Twilley (1988) and Harrison et al. (1997) as per their study higher condition factor was expected during the monsoon, due Northeast monsoon winds increased primary productivity in Arabian Sea. Lower fishing pressure could cause negative allometric growth while the positive allometric growth is the consequence of excessive fishing pressure (Bilgin and Solak, 2020).
CONCLUSION
This study provides baseline information on the growth of marine catfish, A. maculatus from the Arabian Sea. Moreover, the LWR of this commercially important fish provide information for stock assessment and sustainable fisheries management. This work has also highlighted positive and negative allometric growth in natural habitat of this species.
Acknowledgement
I gratefully acknowledge the help of my father named Muhammad Zaman Khan who provided me the samples and helped in fish identification.
Funding
Department of Zoology, University of Karachi, Karachi, Pakistan provided funds and logistics for this study.
Statement of conflict of interest
The authors have declared no conflict of interest.
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