Does this FASTQ data contain single or paired end calls? I have this fastq data from GEO:

zcat SRR1658526.fastq.gz | head -n 20
@SRR1658526.1 HWI-ST398:296:C1MP4ACXX:1:1101:1093:2094 length=102
GATCTCTATTACTTTTTGAAGGATTNNNNNNNNNNAANTTTTGAATCANNNNNNNNNNNNNNNNNNNNNNNNNNNNNTNNNNNNNNNNNNNNNNNNNNNNNN
+SRR1658526.1 HWI-ST398:296:C1MP4ACXX:1:1101:1093:2094 length=102
@&lt;@FFDFDHHFHHIIIIGHBGGGIG##########10#0:BGDDHHII######################################################
@SRR1658526.2 HWI-ST398:296:C1MP4ACXX:1:1101:1167:2107 length=102
ATAATATTGTAGATATAAATGTTATCTAATCTTATCTGATCAGCTTGCTNNATANNNNNNNNNNNNNNNNNNACNTATGNNNNNNNNNNNNNNNNNNNNNCC
+SRR1658526.2 HWI-ST398:296:C1MP4ACXX:1:1101:1167:2107 length=102
CCCFFFFFHHFHHJJIIIIJIJJHJHJJJJIJJIJJJJIJHIJJJJGII#####################################################


It is supposed to be paired-end sequences. Is the prefix @ and + are the R1 and R2? What's the convention here?
Entries in a fastq file occupy 4 lines each and R1 and R2 are typically in different files. Since that SRA project is 2x51 you seem to have run fastq-dump without the --split-3 option, so both R1 and R2 are merged together. Make your life easier and never use SRA, but instead just download the individual files from ENA.