Stock Assessment of Arius maculatus (Thurnberg, 1792) (Ariidae, Siluriformes) in Panguil Bay, Northwestern Mindanao

Arius maculatus, commonly known as spotted catfish and locally known as Tambangongo, has a great potential as an aquaculture species, but there is very limited information known for the stocks in Panguil Bay. This study aimed to assess the wild stocks of A. maculatus, and make an inventory of the fishing boat and gears in two stations in Panguil Bay, namely: Tangub, Misamis Occidental and Baroy, Lanao del Norte. Length frequencies were analyzed to provide estimates of growth, mortality, exploitation ratio, and recruitment pulse of A. maculatus in the bay. A total of 589 boats (324 motorized boats and 265 non-motorized boats) were recorded from the sites. There were 473 units of 15 types of fishing gear used in the sites and 6 types of these were only used in catching A. maculatus. A total of 3,259 specimens were collected for 12 months from the sites. The aquatic habitat of A. maculatus from the two sites was characterized by a pH range of 7.9-8.1, temperature of 28.5-29.1°C, salinity of 13.31-15.9 ppt, dissolved oxygen levels of 4.0-5.41 ppm, and total suspended solid values of 0.1-0.6 g/L. Reproductive biology analysis indicates that eggs start to mature from October to December, then spawning starts from January to March, and the fish fry recruitment starts in April and May. A. maculatus can grow up to 98.95 cm with an asymptotic length of 98.86 cm (K value = 0.35) equivalent to asymptotic weigth of 8,750 g. Mortality Z = 0.99, with natural mortality M = 0.67 and fishing mortality F = 0.33. This study revealed that A. maculatus in Panguil Bay is not over-exploited since the exploitation rate (E = 0.33) is minimal and large individuals can still be collected from the field

Aspects of the reproductive biology of the marine ornamental Vagabond Butterflyfish Chaetodon vagabundus Linnaeus, 1758 (Pisces, Chaetodontidae) from Iligan Bay, Southern Philippines

The reproductive biology of ornamental fish species from coral reefs is poorly studied despite increasing demand in the aquarium trade industry. Aspects of the reproductive biology of the Vagabond butterflyfish, Chaetodon vagabundus Linnaeus, 1758, from Iligan Bay, Southern Philippines were investigated from August 2021 to August 2022. Monthly samples of 30 to 45 individuals per class size with a range of 9 to 14.1 cm (TL) were collected to examine the sex ratio, maturity stages and spawning period, gonadosomatic index (GSI), length at first maturity (L50) and the batch fecundity (BF) of the species. The sex ratio showed female dominance (1:1.42) among size classes and across months. The spawning period indicates a peak during the inter-monsoon or warm months (April and May) and extends beginning of the Southwest monsoon period (June and July). These were supported by the relatively higher gonadosomatic index (GSI) recorded during these months. Histological examination showed that the ovaries during this period had the presence of numerous tertiary vitellogenic and hydrated oocytes and post-ovulatory follicles. At the same time for testes, there are occurrences of dense spermatozoa in the lumen of tubules in testes. This served as confirmatory evidence in support of the spawning period. The length at first sexual maturity of males (10.58 cm TL) was slightly shorter than females (10.91 cm TL). Fecundity increased with the fish’s total length and weight showing a non-linear relationship that was best described by a power function. This study highlighted the valuable data produced that are required for the management of the population stock of this species

Spatio-Temporal Distribution of Ichthyoplankton in Manila Bay in Relation to Oceanographic Conditions

Manila Bay faces serious problems today such as pollution, coastal area reclamation and infrastructure, overfishing, and other activities that worsen the present condition of the bay. It is considered as one of the major fishing grounds in the Philippines. Fish eggs and larvae collection was carried out to determine their distribution, abundance, and composition in the bay. Eight established sampling stations were placed throughout the bay with an average distance of 5-6 nautical miles apart and sampled every other month on a monsoonal basis. Bongo net (360 microns mesh size, 1.5 meters in length, and a diameter of 50-centimeter mouth opening) with attached calibrated flowmeter was used in collecting fish larvae. Physical (salinity, temperature,), chemical (nitrite, nitrate, phosphate, silicate, dissolved oxygen), and biological (phytoplankton, zooplankton) parameters were also carefully studied to be able to explain such uncommon event within the bay. In spite of the current status and worsening condition of water quality of the bay, high abundances of fish eggs and larvae were consistently observed during the northeast monsoon surveys (March) from 2012 to 2015. A total of 3,008 individuals were identified belonging to 34 fish families. The highest fish egg density was observed during March 2013 with 1,550 ind./100m3, followed by March 2012 and 2015 with 1,484 ind./100m3 and 1,182 ind./100m3, respectively. An abundance of fish larvae was observed during March 2015 with 414 ind./100m3, followed by March 2012 (329 ind./100m3), and March 2014 (311 ind./100m3). The lowest density observed was in September 2012 with a density of 132 ind/100m3 fish eggs and 46 ind/100m3 fish larvae. The results were consistent that most fish eggs aggregate in the middle part of the bay especially in Stations 4 and 2 from 2012-2015. For fish larvae, they were consistently found in the eastern part of the bay (stations 6, 8, and 7) throughout the duration of the study, it was also the areas where high concentrations of phytoplankton, zooplankton, and nutrients were observed. A high abundance of fish eggs and fish larvae was observed during northeast monsoon than southwest monsoon. In addition, fish larvae family was dominated by small pelagic fish such as sardines, slipmouths, and mullets. The most dominant fish families found were Clupeidae, followed Leiognathidae, and Nemipteridae. Sillaginidae and Mugilidae were also included in the top five abundant families that occur during every sampling period were

Spatio-Temporal Variability of Zooplankton Distribution and Abundance in Manila Bay from 2013-2015

The study characterized the spatiotemporal variations in composition, abundance, and diversity of zooplankton community in Manila Bay. Zooplankton samples were collected every two months within three years from 2013 to 2015. The zooplankton composition of Manila Bay includes 29, 52, and 50 taxa in 2013, 2014, and 2015, respectively belonging to the following major groups: Copepoda, Decapoda, Cladocera, Chordata, Annelida, Mollusca, Chaetognatha, Ciliophora, Foraminifera, Echinodermata, and Chromista. Copepod nauplii consistently dominated the zooplankton community in the bay from 2013 to 2015 followed by Tintinnids, Oithona spp., Euterpina acutifrons, and Paracalanus spp. The highest concentration of zooplankton was specifically observed in the south western side near the mouth of the bay (Station 4) in July 2015. In 2014, the highest recorded zooplankton density was in the month of November in the eastern side (Station 10). In general, relatively high diversities of zooplankton community were recorded in many months in 2015 as compared to 2013 and 2014 although the highest recorded diversity occurred in March 2014. Redundancy Analysis revealed salinity, temperature, dissolved oxygen, chlorophyll a, PO4, SiO, and NO3 to have a strong correlation with the zooplankton abundances and distribution

Diel patterns of zooplankton community structure in nearshore waters of different substrates off Tinggi and Sibu Islands, Malaysia, with special reference to copepods

The relationship between zooplankton community structure and selected environmental conditions was investigated by simultaneous two-day consecutive sampling in the waters overlying coral and sand sites off Sibu Island and a seagrass site off Tinggi Island, Johor, Malaysia. A total of 129 taxa were identified, 60 non-copepod taxa and 69 copepod species in all samples. Uni- and multi-variate analyses reveal distinct coral, sand, seagrass copepod assemblages with indicator copepod species and attributes of their size fractions. Small fraction (100–335 μm) samples contained greatest number of individuals, few rare species and were densest at onshore depths, and the opposite for large fraction (>335 μm) samples but were densest at nighttime and most species rich in the coral site at night. Higher species diversity at offshore stations is due likely to ecotonal effects of overlapping oceanic and nearshore communities. This study demonstrates the usefulness of uni- and multi-variate analyses in identifying patterns in zooplankton community structure in representative shallow tropical habitats, and the need for accurate zooplankton taxonomy, nighttime and daytime and onshore and offshore sampling, and size fractionation of samples

A new species of Acartia (Copepoda, Calanoida) from the Philippines, based on morphological and molecular analyses

A new species of Acartia (Odontacartia), A. (O.) edentatasp. n., was collected from Leyte Island in the Philippines. Morphologically, the new species resembles A. (O.) pacifica Steuer, 1915. The female of the new species differs from other species of the A. (O.) erythraea Giesbrecht, 1889 species group in the absence of a pair of sharp spines on the posterior border of the genital double-somite and absence of setules on the lateral margins of urosomites 1–3. Unlike other congeners of the species group, males of the new species lack fine setules along the posterior margin of the prosome. Comparison of the new species with A. (O.) pacifica by pairwise distance data for the 16S (282 bp) gene indicates that these species differ by 20–21%, while the COI gene (636 bp) indicates a difference of 16–17%. The new species seems to be a coastal, occurring in warm waters having a salinity of 33.5