Climate variable relate biological respond of tropical fish: A review from small scale fisheries in Sunda Strait

The issue of climate change is currently one of the crucial issues in fisheries management to ensure potential threats and their sustainability. Various approaches have been made, one of which is by looking at the influence of the population biology parameters such as the percentage of gonad maturity, the change from the length at first maturity (Lm50), and the first length of the first capture (Lc50)and growth rate (k). The research conducted from the Sunda Strait sea collected data from 2011, 2015, 2016, 2018, and 2019. The fish species whose biological data were analyzed were turmeric, kurisi and swanggi fish. The analysis performed was the size when 50 percent reached gonad maturity (Lm50), and the size of 50 percent of the fish caught (Lc50), the percentage of fish at the gonad maturity stage (TKG3-4). Annual trend analysis and linear regression determine the relationship between year temperature parameters and Lm, Lc, and the percentage of fish to be fully cooked gonads. The analysis results showed a fluctuation of Lm50, Lc50 in both male and female kurisi, kuniran and swanggi. However, there was no significant correlation between temperature and these parameters. These results indicate that the dynamics of Lm and Lm do not follow the trend of temperature changes. It is assumed that the effect of changes in Lm, Lc is more influenced by the intensity of the catch than the temperature in Sunda Strait.


Introduction
The impact of climate change can be seen from various phenomena on the environment, both on coastal biophysical conditions, ecosystems, and fish resources.The biophysics aspect, such as the sea-level rise and decreasing coastal land (subsidence), is also shown in the coastal.Furthermore, it also has an impact on increasing coastal and sea inundation (rob) and flooding.Impacts on ecosystems include bleaching of coral reef ecosystems, mass mortality of fish, and stirring of water masses.Furthermore, the effects on fish resources include changes in fish life adaptation, effects on biological cycles such as changes in reproductive patterns, and disturbances to biological functions such as sex and fish life changes that become hermaphrodites.In this last section, various studies are being carried out to ascertain the broader impact of temperature changes on fish biology.
In studying the impact of climate change on fish resources, the most studied are aspects of habitat adaptation, biological adaptation.Habitat adaptation is usually the fish looking for suitable niches to grow and get food.At the same time, biological adaptation is to determine the effect on fish growth, fish reproduction, such as time to reach gonad maturity, gonadal size, egg quality.This view is a thesis commonly expressed by many current studies that internal and external factors exist from climate change 1.
In reviewing the thesis, the pattern of daily, monthly, or year fluctuations of these parameters is also studied by looking at the relationship between the reproductive pattern formed and the pattern of temperature changes.This relationship model is then used to strengthen that the temperature trend towards the reproductive trend has the same tendency.
An analysis of several fish resources in the Sunda Strait was then carried out in examining these relationships and relationships.The fish species studied were Kiran, kurisi, and swanggi fish.Turmeric, kurisi, and swanggi fish are demersal fish but live in shallow waters and are associated with corals.Including groups of bottom fish that are phototaxis positive and actively looking for food when there is enough light.
Penetration of deep light due to sunlight also affects the ability to find food.It also encourages stimulation of the reproductive organs in gonad maturation.The intensity of the temperature that is getting stronger enables the fish to reach gonad maturity faster.Based on research 2 , the effect of seawater temperature significantly affects changes in gonad maturity size and the amount of fecundity.
The thesis on the effect of temperature on the reproductive process of fish then becomes the aim of this research.The objective is to analyze the size changes that undergo gonad maturity and the relationship, pattern, and effect of the temperature changes found.Furthermore, this information becomes one of the inputs in regulating the utilization of fish resources by considering the level of gonad maturity.

Research area
The research was conducted from 2011 to 2019 as part of the long-term research of the fisheries resource management division.The sampling location is in the Labuan TPI, which predominantly lands its catch from catching in the Sunda Strait.The research location is as presented in the Figure 1.The data collected is data on sea surface temperature ( o C), data on the maturity level of fish gonads, data on fish length (mm) in that period.The data is then analyzed using a descriptive statistical approach.
2.2.Data analyses 2.2.1.Sea Surface Temperature (SST).Sea surface temperature data was extracted from MODIS level 3 satellite imagery on the website 3 and data visualization.The data processing is carried out in stages, namely data collection, image cutting, and data visualization.The process of cropping the image according to the desired area using SeaDas 7.5.1 software.With a focus on the waters of the Sunda Strait.Temperature analysis is carried out descriptively to see the trend and range of temperature changes obtained.

Length at Age First Maturity (50%).
Determination of the size of the first time kuniran, kurisi and swanggi fish reach gonad maturity can be estimated by the proposed Spearman-Karber method 4.
Then the 95% confidence interval is determined as follows.
m is the logarithm of the length of the fish at the time of first gonad maturity.xk is the logarithm of the last length class mean at the time of first gonad maturity.x is the difference in the logarithm of the increase in length at the mean.pi is the proportion of mature gonadal fish in the I-length class and ni is the number of fish in the i-length class.qi is 1-pi, and Lm is the average length of the first gonadal fish.

Length at first catch.
Estimation of the size of the first fish caught is done by making a graph of the relationship between the distribution of class length (x axis) and the number of fish expressed as a cumulative percentage (y axis), so that a sigmoid curve is formed.The point of intersection between the standard logistic curve with 50% cumulative frequency is considered as the value of the size at first caught (Lc), which is calculated by the following equation 5.
SL is the estimated number of fish caught with fishing gear divided by the total number of fish caught; S1 and S2 are constants a and b.

Growth rate coefficient.
Fish growth parameters can be analyzed using the von Bertalanffy equation 5.
The growth parameters analyzed, namely the values of K and L∞ were estimated using the FISAT II program, the ELEFAN I method.The estimate for the t0 value was obtained from the equation 5.Lt is fish length at age t (mm), Lmm is fish infinity length (mm), K is fish growth coefficient, t0 is theoretical age at zero fish length.

2.2.5.
The relationship between sea surface temperature and changes in reproductive patterns, catch sizes, and fish growth rate coefficients.The relationship between sea surface temperature (SST), reproduction pattern, catch size, and fish growth rate coefficient can be determined by determining the linear correlation coefficient.The correlation coefficient (r) is a measure of the linear correlation between the two variables.The correlation coefficient (r) (Pearson Product Moment) can be determined by the following formula 6.
The value of r is the correlation coefficient of the sample, n is the number of sample observations, x is the variable that affects the sea surface temperature, y is the variable that is affected, namely the reproduction pattern, catch size, and fish growth coefficient.

SST trend
The sea surface temperature values are obtained by MODIS level 3 images on the website 3, the temperature data taken is data from 2010 to 2019.The distribution trend of sea surface temperatures in the Sunda Strait at the time of observation can be seen in Figure 2.

Length at first capture
The size of the first caught fish caught for kuniran fish, males 111.6 mm and females 119.7 mm with an average of 115.64.The first male Kurisi fish caught in size 175.5 mm and the female kurisi fish caught 173.2 mm with an average of 174.38 mm.Meanwhile, the size of the first male swanggi caught was 196.0 mm, and the female swanggi fish was 190.4 mm with an average of 193, 175 mm.The catch size profile of each of these species is presented in Figure 4.The comparison of the results obtained shows that the swanggi fish caught were longer than the kurisi and kuniran fish.This size difference is also influenced by the ability to grow these fish.According to Meichandri 7 that the relationship pattern of length and weight and the conditions of the three types of fish is relatively the same.So it can be presumed that the catch of small-size kuniran fish is due to the physiology of the fish whose growth ability is lower than other fish.

Correlation of SST, Lm50%, Lc50, K and Gonad maturity
The values of Lm50%, Lc50%, K, and the percentage of mature gonadal fish have changes in patterns that are not the same as changes in sea surface temperature.This shows that changes in reproduction patterns, catch size, and growth of demersal fish are not related to the value of sea surface temperature.Based on the t-test with 95% confidence interval, the value of ttest < ttable, so it can be concluded that Lm50%, Lc50%, K, and the percentage of mature gonadal fish in the three fish are not correlated with sea surface temperature.Changes in reproduction patterns, catch sizes, and growth-related to sea surface temperatures of the three fish can be seen in Tables 1, Table 2, Table 3, Table 4, Table 5 and Table 6.
Table 1.The correlation of SPL to Lm50%, Lc50%, K, and TKG (%) of male kuniran fish.In general, the effect of temperature changes on the reproductive parameters of fish in the Sunda Strait is not visible.This means that changes do not always follow temperature changes in the size of the fish reaching gonad maturity, the size of fish commonly caught, the growth rate of fish, and the percentage of fish reaching gonad maturity.The three fish did not show any reaction to reproductive activity due to temperature changes.Some of the possible reasons in the waters of the Sunda strait are fluctuations in sea surface temperature that are not too large (relatively uniform temperature is a maximum of 1.4 o C the difference), and the adaptability of fish to the environment.Another cause of low-temperature fluctuations is the characteristics of the Sunda strait which are influenced by currents from the south (Indian Ocean) on Arlindo and currents from the north (Natuna Sea) when the arlindo reverse current or north currents.As a result, the waters of the Sunda Strait become a mixing area for seawater masses.

Parameters
Mora and Ospina 8 tested on a lab scale on 15 types of reef fish, showing that a temperature fluctuation of 6.1 o C showed that fish were still tolerant of temperature.However, a large range could have an impact on reproduction.Sheaves 9 explained that spawning usually occurs at higher latitudes with more significant sea surface temperatures.Bias, the percentage of spawning fish will increase with an increase in sea surface temperature.This study shows that the largest portion of fish reaching gonad maturity occurred at the optimal temperature of 29.13 o C. The warmer water temperatures in tributaries initiated earlier reproductive activity such as gonad development 10 but not hatching activity.
The temperature increases will affect reproduction 11 in tropical sea.Still, the nature of these effects will depend on the period and amplitude of the rise and range from phase-shifting of spawning to complete inhibition of reproduction.The strong relationship between spawning and temperature was also explained by Asch et al. 12, that spawning began before the bool algae occurred.This means that the influence of eating is not so dominant on the reproductive process occurs.The fish length, and sea temperature during maturation were equally important and together explained about 80% of the spawning time variation 13.Otterson et al 15 increased influence of climate on recruitment through changes in the spawning stock age and size composition is general and might be found in other systems.The increasing influence of climate can be seen from changes in the age of spawning stock, composition in natural structure.

Conclusion
The difference in sea surface temperature found in the waters of the Sunda Strait is relatively low (range less than 2 o C).The low sea surface temperature range in the Sunda Strait is thought to occur due to the interaction of two water masses between the flow from the Indian Ocean in the south and the Natuna Sea in the north.This study found that, in general the reproductive conditions of kuniran, kurisi, and swanggi fish were not affected by changes in temperature in the Sunda Strait, which were relatively low.The low correlation formed indicates that the temperature in the waters of the Sunda Strait is not the main driving factor for changes in reproductive patterns.For this reason, changes in the reproductive patterns of these three types of fish can be evaluated by other factors such as habitat quality, food supply, and fishing pressure.

Figure 4 .
Figure 4. Length at first capture (Lc) of demersal species.