Effects of Habitat-Specific Primary Production on Fish Size, Biomass, and Production in Northern Oligotrophic Lakes

Ecological theory predicts that the relative distribution of primary production across habitats influence fish size structure and biomass production. In this study, we assessed individual, population, and community-level consequences for brown trout (Salmo trutta) and Arctic char (Salvelinus alpinus) of variation in estimated habitat specific (benthic and pelagic) and total whole lake (GPPwhole) gross primary production in 27 northern oligotrophic lakes. We found that higher contribution of benthic primary production to GPPwhole was associated with higher community biomass and larger maximum and mean sizes of fish. At the population level, species-specific responses differed. Increased benthic primary production (GPPBenthic) correlated to higher population biomass of brown trout regardless of being alone or in sympatry, while Arctic char responded positively to pelagic primary production (GPPPelagic) in sympatric populations. In sympatric lakes, the maximum size of both species was positively related to both GPPBenthic and the benthic contribution to GPPWhole. In allopatric lakes, brown trout mean and maximum size and Arctic char mean size were positively related to the benthic proportion of GPPWhole. Our results highlight the importance of light-controlled benthic primary production for fish biomass production in oligotrophic northern lakes. Our results further suggest that consequences of ontogenetic asymmetry and niche shifts may cause the distribution of primary production across habitats to be more important than the total ecosystem primary production for fish size, population biomass, and production. Awareness of the relationships between light availability and asymmetric resource production favoring large fish and fish production may allow for cost-efficient and more informed management actions in northern oligotrophic lakes.

PENILAIAN STATUS DOMAIN SUMBER DAYA IKAN LEMURU DENGAN PENDEKATAN EKOSISTEM YANG DIDARATKAN DI PPI KEDONGANAN, BALI

PPI Kedonganan is a fish landing base located in Kedonganan Village, Kuta District, Badung Regency. One of the fish commodities that landed at PPI Kedonganan is Lemuru Fish (Sardinella lemuru). The high rate of catching Lemuru must be balanced with proper management so that Lemuru Fish Resources remain sustainable. This study was conducted to determine the status of the utilization of Lemuru fish resources. The study was conducted from January 2021 to March 2021. Data collection was carried out by observation and interviews. Data analysis of each indicator was carried out using a multi-criteria analysis approach with composite index assessment and visualization by flag model. Indicators were observed the trends of fish size, the proportion of juvenile fish were caught, the species composition, range collapse of fish resources, Endangered, Threatened, and Protected species. The status assessment of the Lemuru resource domain which landed at PPI Kedonganan is in the good category with a composite value of 66.7. Results of the trend indicators of fish size is relatively fixed, the proportion of fish juvenile caught about 90%, the composition of species caught was 100% of the target fish i.e, lemuru that caught by using gill net, range collapse of fish resources as much as 57% of fishermen expressed relatively fixed in looking for fishing grounds, and ETP species not found. Keywords: EAFM; Lemuru Fish; Fisheries Management; PPI Kedonganan.

Heavy metal accumulation in marine fishes in Porirua Harbour

<p>Heavy metal or metalloids are common pollutants that are discharged into the aquatic environment by a variety of natural and anthropogenic sources, and have the ability to bio- accumulate in the tissues of marine organisms. Fish are among the top consumers in aquatic ecosystems and are widely recognised as bio-indicators for heavy metal pollution. Accumulation of heavy metals is influenced by factors such as species, age, size, and trophic level and can be found in various tissue types, such as muscle and liver tissue. In addition, contaminated fish can pose a threat to human consumers as they can cause acute and chronic disorders. Estuaries are particularly vulnerable to heavy metal pollution as they are as they are a direct recipient of raw sewage, industrial, residential and farming runoff. Estuaries provide essential habitat for a range of species, including fishes that occupy estuaries permanently or seasonally for breeding. Te Awarua-o-Porirua Harbour (Porirua Harbour) is the largest, and the most significant estuary in the southern North Island of New Zealand. It is a 807 hectare tidal lagoon estuary next to Porirua City and consists of two distinct estuary arms, Onepoto and Pauatahanui. Porirua Harbour once boasted a healthy and diverse ecosystem that supported fishes that are prized by the Ngati Toa as kaimoana. However, heavy metal contamination has become problematic following the introduction of intensive industry and development in the harbour catchment. The aim of this research was to 1) quantify levels of four heavy metals (Cu, Zn, Pb, and Hg) in the tissue (muscle and liver) of yellow belly flounder (Pātiki, tōtara, Rhombosolea leporina), sand flounder (Pātiki, Rhombosolea plebeia), speckled sole (Peltorhamphus latus), rig shark (Pioke, Makō, Mangō, Mustelus lenticulatus), short-tailed stingray (Whai, Dasyatis brevicaudata), and eagle ray (Whai keo, Myliobatis tenuicaudatus) caught in Porirua Harbour, and look for differences between sexes, tissue types, as well as effects of size and age, 2) examine each fish sampled for general metrics of health (parasite load, skin lesions, etc.) as well as diet, and look for relationships with body burdens of metals, 3) examine maternal offloading of heavy metals from pregnant rig shark to near-term embryos, 4) examine the movement of benthic fishes between the two estuary arms using mark/recapture methods. To assess heavy metal accumulation and movement in benthic fishes, fish were collected and/or tagged over a 4-month period in 2018 (March-August) across 8 sites in Porirua Harbour. Tagged fish were unable to be recovered so conclusions were left undetermined. Overall, liver tissue had the highest levels of heavy metal concentration, with the expectation of Hg being elevated in the muscle tissue of rig shark. There were significant differences observed for species, fish size, with smaller fishes having higher Cu concentration, and larger fish having higher Hg concentrations. There was little to no relationship observed between Zn and Pb concentrations in this study. To investigate the role of maternal offloading of heavy metals from maternal rig shark to their near-term embryos, embryos were collected from the uterus of 13 pregnant females and assessed individually for heavy metal (Cu, Zn, Pb, Hg) concentrations in muscle tissue. Overall, there was no relationship for Cu between the amount in embryos and either the maternal concentration or size. However, Zn and Pb concentration in rig shark embryos were positively related with maternal size. Therefore, size explained embryo Zn and Pb concentration in rig shark embryos, and embryo Hg concentrations were explained by maternal concentrations and size, suggesting maternal offloading of Hg might be occurring in rig shark. The results of this thesis support prior research findings of heavy metal accumulation depending primarily on the tissue type, fish size and is metal and species specific. This research adds to the currently lacking information on heavy metal accumulation in these study species, and will aid the ongoing monitoring of Porirua Harbour by Greater Wellington Regional Council and Porirua City Council.</p>

Heavy metal accumulation in marine fishes in Porirua Harbour

<p>Heavy metal or metalloids are common pollutants that are discharged into the aquatic environment by a variety of natural and anthropogenic sources, and have the ability to bio- accumulate in the tissues of marine organisms. Fish are among the top consumers in aquatic ecosystems and are widely recognised as bio-indicators for heavy metal pollution. Accumulation of heavy metals is influenced by factors such as species, age, size, and trophic level and can be found in various tissue types, such as muscle and liver tissue. In addition, contaminated fish can pose a threat to human consumers as they can cause acute and chronic disorders. Estuaries are particularly vulnerable to heavy metal pollution as they are as they are a direct recipient of raw sewage, industrial, residential and farming runoff. Estuaries provide essential habitat for a range of species, including fishes that occupy estuaries permanently or seasonally for breeding. Te Awarua-o-Porirua Harbour (Porirua Harbour) is the largest, and the most significant estuary in the southern North Island of New Zealand. It is a 807 hectare tidal lagoon estuary next to Porirua City and consists of two distinct estuary arms, Onepoto and Pauatahanui. Porirua Harbour once boasted a healthy and diverse ecosystem that supported fishes that are prized by the Ngati Toa as kaimoana. However, heavy metal contamination has become problematic following the introduction of intensive industry and development in the harbour catchment. The aim of this research was to 1) quantify levels of four heavy metals (Cu, Zn, Pb, and Hg) in the tissue (muscle and liver) of yellow belly flounder (Pātiki, tōtara, Rhombosolea leporina), sand flounder (Pātiki, Rhombosolea plebeia), speckled sole (Peltorhamphus latus), rig shark (Pioke, Makō, Mangō, Mustelus lenticulatus), short-tailed stingray (Whai, Dasyatis brevicaudata), and eagle ray (Whai keo, Myliobatis tenuicaudatus) caught in Porirua Harbour, and look for differences between sexes, tissue types, as well as effects of size and age, 2) examine each fish sampled for general metrics of health (parasite load, skin lesions, etc.) as well as diet, and look for relationships with body burdens of metals, 3) examine maternal offloading of heavy metals from pregnant rig shark to near-term embryos, 4) examine the movement of benthic fishes between the two estuary arms using mark/recapture methods. To assess heavy metal accumulation and movement in benthic fishes, fish were collected and/or tagged over a 4-month period in 2018 (March-August) across 8 sites in Porirua Harbour. Tagged fish were unable to be recovered so conclusions were left undetermined. Overall, liver tissue had the highest levels of heavy metal concentration, with the expectation of Hg being elevated in the muscle tissue of rig shark. There were significant differences observed for species, fish size, with smaller fishes having higher Cu concentration, and larger fish having higher Hg concentrations. There was little to no relationship observed between Zn and Pb concentrations in this study. To investigate the role of maternal offloading of heavy metals from maternal rig shark to their near-term embryos, embryos were collected from the uterus of 13 pregnant females and assessed individually for heavy metal (Cu, Zn, Pb, Hg) concentrations in muscle tissue. Overall, there was no relationship for Cu between the amount in embryos and either the maternal concentration or size. However, Zn and Pb concentration in rig shark embryos were positively related with maternal size. Therefore, size explained embryo Zn and Pb concentration in rig shark embryos, and embryo Hg concentrations were explained by maternal concentrations and size, suggesting maternal offloading of Hg might be occurring in rig shark. The results of this thesis support prior research findings of heavy metal accumulation depending primarily on the tissue type, fish size and is metal and species specific. This research adds to the currently lacking information on heavy metal accumulation in these study species, and will aid the ongoing monitoring of Porirua Harbour by Greater Wellington Regional Council and Porirua City Council.</p>

Fatty acid profile of pebbly fish, Alestes baremoze (Joannis, 1835) from Lake Albert, Uganda: Implications for its feed requirements

The objective of this study was to establish the fatty acid profile of Alestes baremoze, with a view of establishing its dietary fatty acid requirements. Fish samples from Lake Albert were categorized into four classes according to fork lengths (1–10 cm, 11–20 cm, 21–30 cm, and 31–40 cm), with each class comprising of six fish. In addition, eggs were collected from six sexually mature females. A total of 35 fatty acids were identified and categorized into saturated fatty acids (SFAs), monounsaturated acids (MUFAs), and polyunsaturated fatty acids (PUFAs). SFAs accounted for 5.07% to 37.05%, MUFAs and PUFAs constituted 20.65% to 53.78%, and 10.34% to 66.10% respectively, of total fatty acids in all studied fish size classes. The results from this study indicated that fatty acid composition in A. baremoze varied significantly with size classes. The findings may provide guidance on the fatty acid inclusions for diets formulated for this fish under culture conditions.

​Discrimination of Five Gobid Species (Family: Gobiidae) based on Otolith Morphometry

Background: The fishes of family Gobiidae are one of the least studied fishes, especially for otolith structure. The otoliths were possess species specific features. Hence, traits of sagittal otolith of gobid species studied. Methods: Five gobid species Odontamblyopus roseus (Valenciennes, 1837), Trypauchen vagina (Bloch and Schneider, 1801), Glossogobius giuris (Hamilton, 1822), Parachaeturichthys polynema (Bleeker, 1853) and Boleophthalmus dussumieri (Valenciennes, 1837) were investigated by three methods including morphological, shape indices and step wise discriminant function analysis (SDFA). Result: Interrelationship between shape indices investigated, at 95% level of confidence (P less than 0.05), revealed that perimeter of P. polynema and area of T. vagina have isometric growth with their length (b = 3.0071, 2.90, respectively) and otolith area of B. dussumieri have positive allometric growth (b = 4.23077). SDFA, based on otolith morphometry, discriminated species up with 97.18% accuracy. Hence, the results of present investigation can be used for discrimination of the species and as a tool in predicting fish size from the otoliths and in calculating the biomass of these less studied fish species.

The relationship between fish length and otolith size and weight of Acanthopagrus arabicus Iwatsuki, 2013 (Sparidae) collected from the Iraqi marine waters

Fish specimens (n=75) of A. arabicus were collected from the marine waters of Iraq at Khor al-Zubair. Collection was conducted in the period February–September 2019 at depth of 10–25 m. Relationships between fish length and otolith length, width and weight were calculated for the Arabian yellowfin seabream, Acanthopagrus arabicus using linear models. This study represents the first data available on the relationship of fish size and otolith size and weight for A. arabicus in the Arabian Gulf area. The various relationships between fish length otolith length, width and weight were calculated: Y = -1E – 0.06X2 + 0.0106X + 5.2628, Y = 4E – 06X2 + 0.0077X + 2.1834, and Y = 9E – 07X2 + 0.0013X – 0.191 respectively.

Incorporating antenna detections into abundance estimates of fish

Autonomous passive integrated transponder (PIT) tag antennas are commonly used to detect fish marked with PIT tags but cannot detect unmarked fish, creating challenges for abundance estimation. Here we describe an approach to estimate abundance from paired physical capture and antenna detection data in closed and open mark-recapture models. Additionally, for open models, we develop an approach that incorporates uncertainty in fish size, because fish size changes through time (as fish grow bigger) but is unknown if fish are not physically captured (e.g., only detected on antennas). Incorporation of size uncertainty allows for estimation of size-specific abundances and demonstrates a generally useful method for obtaining state-specific abundances estimates under state uncertainty. Simulation studies comparing models with and without antenna detections illustrate that the benefit of our approach increases as a larger proportion of the population is marked. When applied to two field data sets, our approach to incorporating antenna detections reduced uncertainty in abundance substantially. We conclude that PIT antennas hold great potential for improving abundance estimation, despite the challenges they present.