Exploring the spatial variation of mercury in the Gulf of St. Lawrence using northern gannets as fish samplers

Mercury (Hg) is a ubiquitous and pervasive environmental contaminant with detrimental effects on wildlife, which originates from both natural and anthropogenic sources. Its distribution within ecosystems is influenced by various biogeochemical processes, making it crucial to elucidate the factors driving this variability. To explore these factors, we employed an innovative method to use northern gannets (Morus bassanus) as biological samplers of regurgitated fish in the Gulf of St. Lawrence. We assessed fish total Hg (THg) concentrations in relation to their geographical catch location as well as to pertinent biotic and anthropogenic factors. In small fish species, trophic position, calculated from compound-specific stable nitrogen isotopes in amino acids, emerged as the most influential predictor of THg concentrations. For large fish species, THg concentrations were best explained by δ13C, indicating higher concentrations in inshore habitats. No anthropogenic factors, such as pollution, shipping traffic, or coastal development, were significantly related to THg concentrations in fish. Moreover, previously published THg data in mussels sampled nearby were positively linked with THg concentrations in gannet prey, suggesting consistent mercury distribution across trophic levels in the Gulf of St. Lawrence. Our findings point to habitat-dependent variability in THg concentrations across multiple trophic levels. Our study could have many potential uses in the future, including the identification of vulnerability hotspots for fish populations and their predators, or assessing risk factors for seabirds themselves by using biologically relevant prey.

Radioecological behaviour of 137Cs in rockfish of the southern coastal waters off Fukushima during 2017-2021

Following the accident at the Fukushima Dai-ichi Nuclear Power Station, radiocaesium concentrations were specifically elevated in rockfish species compared to other fish species. To clarify the likely reasons, a caesium metabolic rate in the Japanese rockfish Sebastes cheni was derived by an aquarium experiment of live fish collected from the area off Fukushima. Stable caesium and 137Cs concentration in prey organisms, stomach contents and muscle of rockfish were measured and the bioavailable fraction in prey organisms was evaluated. Using derived transfer parameters, 137Cs radioactivity levels in S. cheni and prey organisms were simulated by a model, and verified by the measured radioactivity concentrations of biota in coastal waters south of the Fukushima Dai-ichi Nuclear Power Station. As a result, slow caesium metabolism in S. cheni was confirmed with the biological half-life (Tb1/2) of 190 d. The determining factor for the initial 137Cs radioactivity levels in S. cheni, was the maximum radioactivity levels in surrounding seawater which was constrained by the sedentary nature of rockfish. Controlling factors of depuration rate of 137Cs levels in S. cheni were slow caesium metabolism, enhanced 137Cs radioactivity level of prey organisms, and survival of older contaminated individuals due to a long life-span. During the study period 2017-2021, 137Cs radioactivity concentrations in seawater decreased close to the level measured before 2010, whereas those in prey organisms and rockfish in southern Fukushima waters were still above the levels that existed before 2010. An additional source for enhancing 137Cs radioactivity in rockfish and biota of the food chain was indicated by the greater 137Cs/133Cs atom ratios in rockfish compared to those in the surrounding seawater, however it was considered to be radiologically insignificant in relation to seafood safety limits.

Rapid turnover and evolution of sex-determining regions in Sebastes rockfishes

Nature has evolved a wealth of sex determination (SD) mechanisms, driven by both genetic and environmental factors. Recent studies of SD in fishes have shown that not all taxa fit the classic paradigm of sex chromosome evolution and diverse SD methods can be found even among closely related species. Here, we apply a suite of genomic approaches to investigate sex-biased genomic variation in eight species of Sebastes rockfish found in the northeast Pacific Ocean. Using recently assembled chromosome-level rockfish genomes, we leverage published sequence data to identify disparate sex chromosomes and sex-biased loci in five species. We identify two putative male sex chromosomes in S. diaconus, a single putative sex chromosome in the sibling species S. carnatus and S. chrysomelas, and an unplaced sex determining contig in the sibling species S. miniatus and S. crocotulus. Our study provides evidence for disparate means of sex determination within a recently diverged set of species and sheds light on the diverse origins of sex determination mechanisms present in the animal kingdom.

Identification and characterization of lipocalin-type prostaglandin D2 synthase homologs in the urine of male rockfish

Black rockfish (Sebastes schlegelii) and its relatives are viviparous marine fish. Males produce urinary proteins during the copulation season; however, the identity of these proteins was unknown. In this study, we focused on high-molecular-weight urinary proteins (HMWups) in male black rockfish. The HMWups were identified by liquid chromatography and tandem mass spectrometry (LC-MS/MS) of urine. In silico analyses of RNA-seq data predicted the tissue distribution of candidate HMWup transcripts and their gene structures. Candidate cDNAs were cloned and a recombinant protein of a major candidate was prepared. Western blotting of urine using an antiserum against the recombinant protein was performed to reconfirm the LC-MS/MS results. Quantitative real-time polymerase chain reaction (qRT-PCR) and immunohistochemistry were employed to validate the prediction by RNA-seq and identify the cells producing HMWups, respectively. LC-MS/MS, in conjunction with Western blotting and cDNA cloning, identified the HMWups as lipocalin-type prostaglandin D₂ synthase (l-PGDS) homologs. RNA-seq analyses and qRT-PCR revealed that the l-PGDS homolog transcripts were dominantly expressed in the testis and male kidney; Sertoli cells and epithelial cells in the renal tubules were immunoreactive. These results indicated that major protein components in the urine of male black rockfish are l-PGDS homologs, potentially produced by the renal tubules in the kidney. Male rockfish (genus Sebastes) are thought to release unknown pheromone substances during mating behavior. The knowledge and tools obtained in this study empower research into the role(s) of HMWups in pheromone systems underlying rockfish reproduction. No protein-type teleost pheromone has heretofore been discovered.

Elucidating the acid-base mechanisms underlying otolith overgrowth in fish exposed to ocean acidification

Over a decade ago, ocean acidification (OA) exposure was reported to induce otolith overgrowth in teleost fish. This phenomenon was subsequently confirmed in multiple species; however, the underlying physiological causes remain unknown. Here, we report that splitnose rockfish (Sebastes diploproa) exposed to ~1600 μatm pCO₂(pH ~7.5) were able to fully regulated the pH of both blood and endolymph (the fluid that surrounds the otolith within the inner ear). However, while blood was regulated around pH 7.80, the endolymph was regulated around pH ~8.30. These different pH setpoints result in increased pCO₂diffusion into the endolymph, which in turn leads to proportional increases in endolymph [HCO₃^-] and [CO₃^2-]. Endolymph pH regulation despite the increased pCO₂suggests enhanced H⁺removal. However, a lack of differences in inner ear bulk and cell-specific Na⁺/K⁺-ATPase and vacuolar type H⁺-ATPase protein abundance localization pointed out to activation of preexisting ATPases, non-bicarbonate pH buffering, or both, as the mechanism for endolymph pH-regulation. These results provide the first direct evidence showcasing the acid-base chemistry of the endolymph of OA-exposed fish favors otolith overgrowth, and suggests that this phenomenon will be more pronounced in species that count with more robust blood and endolymph pH regulatory mechanisms.

KRF-7 isolated from the intestine of rockfish and effects of dietary supplementation with mannan oligosaccharide in rockfish aquaculture

The purpose of this study was to characterize the bacteria isolated from rockfish intestines and to investigate the effects of feed supplementation in rockfish aquaculture. Bacillus sp. KRF-7 isolated from the intestine of rockfish (Sebastes schlegelii) was demonstrated to be safe based on in vitro tests confirming the absence of hemolysis, cytotoxicity, and genes with toxigenic potential. In a feeding trial, providing a supplemental diet of 1 × 10⁸ CFU g^-1Bacillus sp. KRF-7 was observed to positively alter the weight gain, specific growth rate, feed conversion ratio, and protein efficiency ratio of juvenile rockfish. KRF-7 supplementation showed positive regulation of nonspecific immune parameters, such as superoxide dismutase, lysozyme activity, and myeloperoxidase activity. This analysis also revealed a change in the composition of the intestinal microbiota at the phylum level from Proteobacteria to Firmicutes. In both the kidney and spleen, the expression levels of IL-10, NF-κB, and B cell activating factors in the KRF-7-supplemented group were significantly increased compared to those in the control group. Therefore, this study verified the safety of KRF-7 isolated from the intestine of rockfish and suggests that dietary supplementation with KRF-7 enhances the growth performance of rockfish and has beneficial effects on the regulation of the intestinal microbiota and immune response.

Molecular characterization of fshb and lhb subunits and their expression profiles in captive white-edged rockfish, Sebastes taczanowskii

Fundamental knowledge on the regulation of reproduction by gonadotropins (Gths) is quite limited in viviparous fishes. In the present study, we performed molecular cloning and characterization of cDNAs encoding two Gth subunits (fshb and lhb) from the pituitaries of viviparous white-edged rockfish, Sebastes taczanowskii; expression profiles of both gene transcripts were elucidated in the pituitaries of reproductive males and females which were kept in a captive environment. The cloned fshb and lhb fragments exhibited high sequence identities with corresponding β-subunit sequences from black rockfish, S. schlegelii. Notably, the fshb of white-edged rockfish appeared to lack a putative N-glycosylation site, whereas lhb conserved it. Expression of fshb and lhb transcripts in the rockfish pituitaries largely changed in synchrony but for minor exceptions. In males, levels of both transcripts increased with progression of spermatogenesis, although the peak for fshb (October) appeared slightly earlier than that for lhb (November). In females, both gene transcripts exhibited synchronous bimodal changes. High expression of fshb and lhb transcripts in the female pituitary during the gestation period, followed by the drastic decrease at parturition, suggest their possible involvement in regulation of gestation of this species. The knowledge gained for Sebastes in this study superimposes fundamental information necessary for further physiological understanding of viviparity in teleost fish.

Effects of sulfated polysaccharides isolated from Codium fragile on inflammatory cytokine gene expression and Edwardsiella tarda infection in rockfish, Sebastes schlegelii

Sulfated polysaccharides (SPs) derived from Codium fragile (sponge seaweed) can regulate cytokine expression in mammalian macrophages, NK cell lines and olive flounder head kidney primary cells in vitro. In this study, we found that SPs from C. fragile exhibited anti-bacterial activities against fish pathogenic bacteria including Streptococcus parauberis, Lactococcus garvieae, Aeromonas salmonicida and Edwardsiella tarda at a minimum inhibitory concentration of 2 mg/mL, but not against S. iniae or Vibrio anguillarum. Immunostimulatory effects of SPs from C. fragile on rockfish (Sebastes schlegelii) were evaluated by analyzing mRNA expression levels of inflammatory cytokines (interleukin (IL)-1β, IL-8, IL-6 and tumor necrosis factor (TNF)-α) and anti-inflammatory cytokines (IL-10) both in vitro and in vivo. Results revealed that expression levels of all genes tested were upregulated in rockfish head kidney and spleen cells by SPs from C. fragile in a dose/time-dependent manner in vitro. By contrast, expression levels of these genes were significantly (p < 0.05) downregulated in the head kidney and spleen of rockfish in vivo at 1 and 3 days post intraperitoneal injection of SPs from C. fragile. In the liver, these genes were downregulated on day 1, but upregulated on day 3. Treatment with SPs downregulated the expression of these genes in spleen, but upregulated IL-10 gene expression in the intestine and liver. Meanwhile, when fish were fed with crude SPs for 4 weeks and challenged with E. tarda, infected fish started to die starting from 2 days after immune challenge. The cumulative mortality of the 0.1% group was significantly lower (p < 0.05) than that of the control group without feeding with SPs. Expression levels of IL-1β and IL-6 genes were significantly (p < 0.05) upregulated in head kidney of the 0.5% group on day 1 while IL-1β gene expression was downregulated on day 3 in the liver. These results indicate that SPs from C. fragile can regulate the immune gene expression in rockfish and that a diet containing 0.1% crude SPs can reduce the mortality of rockfish caused by E. tarda infection.

The sources and prevalence of anthropogenic noise in Rockfish Conservation Areas with implications for marine reserve planning

Underwater noise pollution is a recognized threat to marine life. In British Columbia, Canada, Pacific rockfish (Sebastes spp.) were historically overfished, prompting the establishment of Rockfish Conservation Areas (RCAs). However, there are no restrictions prohibiting vessel transits in RCAs. We hypothesized that RCAs do not protect rockfish from sub-lethal harm from noise. We compared noise levels at three RCAs with adjacent unprotected reference sites from August 2018-June 2019. While RCAs had lower levels of noise overall than reference sites, this trend was inconsistent; some RCA sites had higher levels of noise during certain time periods than non-RCA sites. A vessel noise detector was the best predictor of noise level over three frequency bands (20-100 Hz, 100-1000 Hz, 1-10 kHz), and predicted sound levels which could mask rockfish communication. We conclude that RCAs do not reliably protect rockfish from noise pollution, and recommend further study into potential impacts on stock recovery.

Molecular, transcriptional and functional delineation of Galectin-8 from black rockfish (Sebastes schlegelii) and its potential immunological role

Galectins are β-galactoside-binding lectins, which are involved in pattern recognition, cell adhesion, and stimulation of the host innate immune responses against microbial pathogens. In spite of several functional studies on different galectins isolated from vertebrates and invertebrates, this is the first report to present functional studies for galectin-8 from the marine teleost tissues. In the present study, we characterized galectin-8 homolog from black rockfish (Sebastes schlegelii), in molecular and functional aspects. Rockfish galectin-8 (SsGal8) was found to consist of a 969 bp long open reading frame (ORF), encoding a protein of 322 amino acids and the predicted molecular weight was 35.82 kDa. In silico analysis of SsGal8 revealed the presence of two carbohydrate binding domains (CRDs), at both N and C-termini and a linker peptide of 40 amino acids, in between the two domains. As expected, the phylogenetic tree categorized SsGal8 as a tandem-repeat galectin, and ultimately positioned it in the sub-clade of fish galectin-8. rSsGal8 was able to strongly agglutinate fish erythrocytes and the inhibition of agglutination was successfully exhibited by lactose and d-galactose. Bacterial agglutination assay resulted in agglutination of both Gram (+) and Gram (-) bacteria, including Escherichia coli, Vibrio harveyi, Vibrio parahaemolyticus, Streptococcus parauberis, Lactococcus garvieae, Streptococcus iniae and Vibrio tapetis. The tissue distribution analysis based on qPCR assays, revealed a ubiquitous tissue expression of SsGal8 for the examined rockfish tissues, with the most pronounced expression in blood, followed by brain, intestine, head kidney and kidney. Furthermore, the mRNA transcription level of SsGal8 was significantly up-regulated in spleen, liver and head kidney, upon immune challenges with Streptococcus iniae, LPS and poly I:C, in a time dependent manner. Taken together, these findings strongly suggest the contribution of SsGal8 in regulating innate immune responses to protect the rockfish from bacterial infections.

Ichthyophonus in sport-caught groundfishes from southcentral Alaska

This report of Ichthyophonus in common sport-caught fishes throughout the marine waters of southcentral Alaska represents the first documentation of natural Ichthyophonus infections in lingcod Ophiodon elongates and yelloweye rockfish Sebastes ruberrimus. In addition, the known geographic range of Ichthyophonus in black rockfish S. melanops has been expanded northward to include southcentral Alaska. Among all species surveyed, the infection prevalence was highest (35%, n = 334) in Pacific halibut Hippoglossus stenolepis. There were no gross indications of high-level infections or clinically diseased individuals. These results support the hypothesis that under typical conditions Ichthyophonus can occur at high infection prevalence accompanied with low-level infection among a variety of fishes throughout the eastern North Pacific Ocean, including southcentral Alaska.

Toxic effects on bioaccumulation and hematological parameters of juvenile rockfish Sebastes schlegelii exposed to dietary lead (Pb) and ascorbic acid

Juvenile rockfish, Sebastes schlegelii (mean length 11.3 ± 1.2 cm, and mean weight 32.5 ± 4.1 g) were exposed for four weeks to dietary lead (Pb²⁺) at 0, 120, and 240 mg/L and ascorbic acid (AsA) at 100, 200, and 400 mg/L. The exposure concentrations and duration of significant Pb-induced accumulations in specific tissues of S. schlegelii were assessed. High levels of ascorbic acid significantly attenuated accumulations following exposure to dietary Pb. Dietary Pb exposure caused a significant increase in blood Pb concentrations, whereas red blood cell (RBC) count, hematocrit, and hemoglobin were significantly decreased. Notable changes were also observed in plasma calcium, magnesium, glucose, cholesterol, glutamic oxaloacetic transaminase (GOT), and glutamic pyruvate transaminase (GPT). The growth performance of S. schlegelii was significantly decreased. High doses AsA supplemention were effective in attenuating the changes brought about by dietary Pb exposure.

The immune responses and expression of metallothionein (MT) gene and heat shock protein 70 (HSP 70) in juvenile rockfish, Sebastes schlegelii, exposed to waterborne arsenic (As3+)

Juvenile rockfish, Sebastes schlegelii (mean length 16.4±1.9cm, and mean weight 71.6±6.4g) were exposed for 20days with the different levels of waterborne arsenic concentration (0, 50, 100, 200 and 400μg/L). The plasma cortisol of S. schlegelii was significantly increased by the waterborne arsenit exposure. In the immune responses, the immunoglobulin M (Ig M) and lysozyme activity of S. schlegelii were significantly increased by the waterborne arsenic exposure. The acetylcholinesterase (AChE) activity of S. schlegelii was inhibited by the waterborne arsenic exposure. The substantial increases in the gene expression such as metallothionein (MT) and heat shock protein 70 (HSP 70) were observed by the waterborne arsenic exposure. The results demonstrated that waterborne arsenic exposure can induce the significant alterations in the immune responses and specific gene expression of S. schlegelii.

The immune responses in juvenile rockfish, Sebastes schlegelii for the stress by the exposure to the dietary lead (II)

The aim of this study was to evaluate the lead toxic effects on the stress parameters and immune responses of Sebastes schlegelii. Juvenile rockfish, S. schlegelii (mean length 14.2±1.9cm, and mean weight 57.3±5.2g) were exposed for 4 weeks with the different levels of dietary lead (Pb(2+)) at 0, 30, 60, 120 and 240mg/L. The plasma cortisol and heat shock protein 70 was evaluated as stress indicators. The plasma cortisol of S. schlegelii was significantly increased in response to the dietary lead exposure over 60mg/kg at 2 weeks. After 4 weeks, the significant increase in the plasma cortisol was observed at 30 and 60mg/kg, but the level was decreased over 120mg/kg. The heat shock protein 70 of S. schlegelii was also notably elevated over 60mg/kg for 4 weeks. In the immune response, the immunoglobulin M of S. schlegelii was considerably increased over 120mg/kg for 4 weeks. A significant increase was observed in lysozyme activity. The plasma lysozyme activity of S. schlegelii was elevated over 120mg/kg after 2 weeks and 60mg/kg after 4 weeks, and kidney lysozyme activity was also increased at 240mg/kg after 2 weeks and over 120mg/kg after 4 weeks. The results indicate that dietary Pb exposure can cause a significant stress and immune stimulation of S. schlegelii.

Molecular structure and immune-stimulated transcriptional modulation of the first teleostean IFP35 counterpart from rockfish (Sebastes schlegelii)

Interferons (IFNs) and IFN-inducible proteins play numerous physiological roles, particularly in antiviral defense mechanisms of the innate immune response with the presence of pathogens. IFN-induced protein-35 kDa (IFP35) is induced by Type II IFN (IFN-γ); it is a cytoplasmic protein that can be translocated to the nucleus via the stimulation of IFN. In this study, we report the complete molecular characterization of the IFP35 cDNA sequence from the black rockfish in an effort to understand its role in the immune response. The coding sequence of RfIFP35 encoded a putative peptide of 371 amino acids containing two characteristic Nmi/IFP 35 domains (NIDs), which are highly conserved among its counterparts. The protein showed a molecular mass of 42.2 kDa with a theoretical pI of 5.05 and was predicted to be unstable because of its high instability index (49.37). Therefore, the protein-protein interaction is essential for its stability, which may be facilitated by the intrinsically disordered regions in this protein. According to cellular location prediction, the RfIFP35 protein is cytosolic. Phylogenetic analysis showed that RfIFP35 was cladded within the fish counterparts. Tissue distribution profiling revealed a ubiquitous presence of the protein in all examined tissues, with highest expression in the blood followed by the spleen tissues. The expression of RfIFP35 during immune challenge with poly I:C and lipopolysaccharide treatments affirms its putative importance in the first-line host defense system. RfIFN-γ mRNA was significantly expressed at 6 h p.i. in blood and 3 h p.i. in the spleen following treatment with different immune stimulants, and its expression was higher compared to that of RfIFP35 mRNA. Therefore, the modulation patterns of both RfIFP35 and RfIFN-γ suggest that RfIFP35 may be induced by RfIFN-γ.

A thioredoxin domain-containing protein 12 from black rockfish Sebastes schlegelii: Responses to immune challenges and protection from apoptosis against oxidative stress

Thioredoxin (TXN) superfamily proteins are identified by the presence of a thioredoxin active site with a conserved CXXC active motif. TXN members are involved in a wide range of biochemical and biological functions including redox regulation, refolding of disulfide containing proteins, and regulation of transcription factors. In the present study, a thioredoxin domain-containing protein 12 was identified and characterized from black rockfish, Sebastes schlegelii (RfTXNDC12). The full length of RfTXNDC12 consists of a 522-bp coding region encoding a 173-amino acid protein. It has a 29-amino acid signal peptide and a single TXN active site with a consensus atypical WCGAC active motif. Multiple sequence alignment revealed that the active site is conserved among vertebrates. RfTXNDC12 shares highest identity with its Epinephelus coioides homolog. Transcriptional analysis revealed its ubiquitous expression in a wide range of tissues with the highest expression in the ovary. Immune challenges conducted with Streptococcus iniae and poly I:C caused upregulation of RfTXNDC12 transcript levels in gills and peripheral blood cells (PBCs), while lipopolysaccharide injection caused downregulation of RfTXNDC12 in gills and upregulation in PBCs. Similar to TXN, RfTXNDC12 exhibited insulin disulfide reducing activity. Interestingly, the recombinant protein showed significant protection of LNCaP cells against apoptosis induced by H2O2-mediated oxidative stress in a concentration dependent manner. Collectively, the present data indicate that RfTXNDC12 is a TXN superfamily member, which could function as a potential antioxidant enzyme and be involved in a defense mechanism against immune challenges.

The toxic effects on the stress and immune responses in juvenile rockfish, Sebastes schlegelii exposed to hexavalent chromium

Juvenile Sebastes schlegelii (mean length 13.7±1.7cm, and mean weight 55.6±4.8g) were exposed for 4 weeks with the different levels of dietary chromium (Cr(6+)) concentration (0, 30, 60, 120 and 200mg/L). The plasma cortisol and heat shock protein 70 was evaluated as stress indicators. Plasma cortisol was significantly increased in response to the dietary chromium exposure over 120mg/kg at 2 and 4 weeks. Heat shock protein 70 was also notably increased over 120mg/kg at 2 weeks and over 60mg/kg at 4 weeks. In the immune response, immunoglobulin M was considerably increased in the concentration of 240mg/kg at 2 weeks and over 120mg/kg at 4 weeks. Lysozyme activity was considerably induced by the dietary hexavalent chromium exposure. A significant increase in plasma lysozyme activity was observed at 240mg/kg after 2 weeks and over 60mg/kg after 4 weeks, kidney lysozyme was also increased over 120mg/kg at 2 and 4 weeks. The results demonstrate that dietary Cr exposure can induce a significant stress and immune stimulation.

Oxidative stress, neurotoxicity, and metallothionein (MT) gene expression in juvenile rock fish Sebastes schlegelii under the different levels of dietary chromium (Cr(6+)) exposure

Juvenile Sebastes schlegelii were exposed for 4 weeks with the different levels of dietary chromium (Cr(6+)) concentration (0, 30, 60, 120 and 200mg/kg). The superoxide dismutase (SOD) activity, glutathione S-transferase (GST) activity, and glutathione (GSH) level of liver and gill were evaluated after 4 weeks exposure. The SOD and GST activity of liver and gill was significantly increased in the concentration of 240mg/kg after 2 weeks and over 120mg/kg after 4 weeks, whereas a considerable decrease in the concentration of 240mg/kg after 2 weeks and over 120mg/kg after 4 weeks was observed in the GSH levels of liver and gill. In neurotoxicity, AChE activity was significatly inhibited in brain in the concentration of 240mg/kg after 2 weeks and over 60mg/kg after 4 weeks and muscle in the concentration of 240mg/kg after 2 weeks and over 120mg/kg after 4 weeks. Metallothionein (MT) gene in liver was considerably increased over 120mg/kg after 2 weeks and at 30, 120, and 240mg/kg after 4 weeks by dietary chromium exposure. The results indicate that dietary Cr exposure over 120mg/kg can induce substantial alterations in antioxidant responses, AChE activity and MT gene expression.

Testing hypotheses in macroevolution

Experimental manipulation of microevolution (changes in frequency of heritable traits in populations) has shed much light on evolutionary processes. But many evolutionary processes occur on scales that are not amenable to experimental manipulation. Indeed, one of the reasons that macroevolution (changes in biodiversity over time, space and lineages) has sometimes been a controversial topic is that processes underlying the generation of biological diversity generally operate at scales that are not open to direct observation or manipulation. Macroevolutionary hypotheses can be tested by using them to generate predictions then asking whether observations from the biological world match those predictions. Each study that identifies significant correlations between evolutionary events, processes or outcomes can generate new predictions that can be further tested with different datasets, allowing a cumulative process that may narrow down on plausible explanations, or lead to rejection of other explanations as inconsistent or unsupported. A similar approach can be taken even for unique events, for example by comparing patterns in different regions, lineages, or time periods. I will illustrate the promise and pitfalls of these approaches using a range of examples, and discuss the problems of inferring causality from significant evolutionary associations.

Noise-Dependent Fish Distribution in Kelp Beds

The marine marbled rockfish Sebastiscus marmoratus is dependent on kelp beds and rocks for survival and reproduction. We found that sound production and hearing sensitivity in S. marmoratus are closely matched in the frequency domain. We also found that the juvenile rockfish prefers the habitat of the larger macroalgae Sargassum horueri rather than the habitat containing the smaller algae Ulva pertusa where the adult rockfish prefers to live. Our underwater noise recording data from these two habitats indicate that their spectra of the background noise have different values. The results suggest that the acoustic cues may be critical for pelagic larvae when selecting the preferential habitat in which to settle.

The chromium accumulation and its physiological effects in juvenile rockfish, Sebastes schlegelii, exposed to different levels of dietary chromium (Cr(6+)) concentrations

Juvenile rockfish (mean length 13.7±1.7 cm, and mean weight 55.6±4.8 g) were exposed for 4 weeks with the different levels of dietary chromium (Cr(6+)) at 0, 30, 60, 120 and 240 mg/kg. The profile of chromium in the tissues of rockfish is dependent on the exposure periods and chromium concentration. After 4 weeks, the order of chromium accumulation in tissues was liver>kidney>spleen>intestine>gill>muscle. The dietary chromium exposure decreased the growth rate and hepatosomatic index of rockfish. The major hematological findings were significant decrease in the red blood cell (RBC) count, hematocrit (Ht) value, and hemoglobin (Hb) concentration exposed to ≥120 mg/kg chromium concentrations. The dietary chromium exposure (≥120 mg/kg) led to notable increase in glucose, cholesterol, glutamic oxalate transaminase (GOT), and glutamic pyruvate transaminase (GPT) in plasma, whereas there was no considerable change in calcium, magnesium, total protein, and alkaline phosphatase (ALP). The results indicated that the dietary chromium exposure to rockfish can induce significant chromium accumulation in the specific tissues, inhibition of growth, and hematological alterations.

The toxic effects of ammonia exposure on antioxidant and immune responses in Rockfish, Sebastes schlegelii during thermal stress

Rockfish, Sebastes schlegelii (mean weight 14.53 ± 1.14 cm, and mean weight 38.36 ± 3.45 g) were exposed for 4 weeks (2 weeks and 4 weeks) with the different levels of ammonia in the concentrations of 0, 0.1, 0.5, 1.0mg/L at 19 and 24°C. The ammonia exposure induced significant alterations in antioxidant responses. The activities of SOD, CAT, and GST were considerably increased by the ammonia exposure depending on water temperature, whereas the GSH level was notably decreased after 2 and 4 weeks. In the stress indicators, the cortisol and HSP 70 were significantly elevated by the exposure to ammonia depending on water temperature. In innate immune responses, the phagocytosis and lysozyme activity were notably decreased by ammonia exposure depending on water temperature after 2 and 4 weeks. The results suggest that ammonia exposure depending on water temperature can induce the considerable alterations in antioxidant responses, stress, and immune inhibition.

Modeling fish production for southern California's petroleum platforms

California's oil platforms are nearing the end of their productive lives and therefore will be decommissioned in the near future. These structures have been shown to be important habitats for both settlement and growth for reef fishes. Important information on the biological effects (i.e., loss of biomass and production) of different decommissioning options has not yet been explored in detail. An important step in the assessment of these different decommissioning options is to look at the potential loss of fish production and habitat under the different alternatives. Using the large amount of information available on fish abundances at these structures, we have created a model to estimate the standing stock of fishes and production that would be lost because of both partial (removal from surface to 85 ft) and complete removal (the 2 decommissioning options being considered). Complete removal of a platform will likely eliminate most of its fish biomass; however, this study has shown that for rockfishes, which settle predominantly below 85 feet (26 m) and move deeper as they age, partial removal through topping would leave more than 90% of the fish biomass at the deeper platforms. Modeling of larval dispersal suggests that platforms provide an important opportunity for recruitment of fish larvae and that many larvae produced near the platforms would settle elsewhere in the region. The results presented here indicate that, even if topped, the potential contribution of platform habitat to biological resources (e.g., fish production) in this region is significant.

The lead accumulation and hematological findings in juvenile rock fish Sebastes schlegelii exposed to the dietary lead (II) concentrations

Juvenile rockfish (mean length 14.2 ± 1.9 cm, and mean weight 57.3 ± 5.2g) were exposed for 4 weeks with the different levels of dietary lead (Pb(2+)) at 0, 30, 60, 120 and 240 mg/L. The exposure concentration and period of Pb have induced significant amount of it the specific tissues of rockfish. The highest Pb accumulation was observed in the kidney tissue by the dietary lead exposure. The growth rate and hepatosomatic index were considerably inhibited over 120 mg/kg. The hematological parameters such as red blood cell (RBC) counts, hematocrit (Ht) value, and hemoglobin (Hb) concentration were significantly decreased over 60 mg/kg Pb concentration. In the inorganic components, the values of calcium and magnesium in plasma were significantly decreased. The glucose and cholesterol values were notably increased, whereas total protein was decreased. The enzyme components, glutamic oxalate transaminase (GOT) and glutamic pyruvate transaminase (GPT), were significantly elevated by the dietary lead exposure, but no change was observed in alkaline phosphatase (ALP).

The arsenic accumulation and its effect on oxidative stress responses in juvenile rockfish, Sebastes schlegelii, exposed to waterborne arsenic (As3+)

Juvenile rockfish (mean length 16.4 ± 1.9 cm, and mean weight 71.6 ± 6.4 g) were exposed for 20 days with the different levels of waterborne arsenic concentration (0, 50, 100, 200 and 400 μg/L). The profile of As accumulation among tissue of rockfish is dependent on the exposure periods and As concentration. After 4 weeks, the highest accumulation of As was observed in the kidney, and the order of As accumulation in tissues was liver > kidney > spleen > gill > intestine > muscle. Generally, significant As accumulation increase in most tissues was observed at the higher concentration of 200 μg/L waterborne As exposure, whereas there was no considerable increase in muscle except the concentration of 400 μg/L at 20 days. In oxidative stress indicators, liver and gill superoxide dismutase (SOD) activity and glutathione-S-transferase (GST) activity were considerably increased after the 20 days exposure. Glutathione (GSH) level in liver and gill was also notably increased in response to the waterborne As exposure after 20 days. The results demonstrated that waterborne As exposure can induce considerable As accumulation in major tissues and alterations in antioxidant enzyme parameters of experimental fish, rockfish.